[bug]: getting `FAILURE_REASON_NO_ROUTE` when I do have sufficient balance in each channel along the route.

[ZZiigguurraatt]

I have the following network:

         TA         SAT            SAT         SAT
 alice <----> bob <----> charlie <----> dave <----> edward

and I'm getting FAILURE_REASON_NO_ROUTE when I do have sufficient balance in each channel along the route. Here is an example output from my test script:

edward sending sats and alice receiving 35400.0 Asset1_base (354.0 Asset1_friendly) via bob
MaxAllowableFee: 11
public channels edward knows about:
dave(EEE) <---- 1000000 sat ----> charlie(EEE)
dave(EEE) <---- 1000000 sat ----> edward(EEE)

accepted_buy_quote {
  peer: "03a157fa253384f49df1343eb4d8ed20fb000dd04abb4f1a519306facb216fe3c3"
  id: "\227\325\032p\036\216\306\350X\270I\325\006\346>\236\022\001O\006\361\022Yo\364\375\262\033\355\256\336\202"
  scid: 17653461947383733890
  asset_max_amount: 35400
  ask_asset_rate {
    coefficient: "9852216748"
  }
  expiry: 1739767738
  min_transportable_units: 34876
}
invoice_result {
  r_hash: "$U[!\0321\321\021\300\014\207\253\214K\334dn\037C\360\342\027\376\310pn9\233N\177\240\212"
  payment_request: "lnbcrt3593100p1pnm90uhpp5y324kgg6x8g3rsqvs74ccj7uv3hp7slsugtlajrsdcueknnl5z9qdqqcqzzsxqyz5vqrzjqws40739xwz0f803xsltfk8dyrasqrwsf2a57xj3jvr04jepdl3u8a8akgd7mtk7sgqqqqlgqqqqqqgq2qsp55hqp6h75hhzum7psxdyc46xny9443skev0ls9hxm8yfpcmhx88us9qxpqysgqys8ukxksxmn6jrsulxqt83e3e4tde0ekjw8p2hartt0tq8xvtw6hrvmfwtaugyxvvpdytpz2r4uduv3jwuc3ed95dz2jqe9q8cu8gxqquv6vkq"
  add_index: 101
  payment_addr: "\245\300\035_\324\275\305\315\37003I\212\350\323!kX\302\331c\377\002\334\3339\022\034n\3469\371"
}

r_hash: 24555b211a31d111c00c87ab8c4bdc646e1f43f0e217fec8706e399b4e7fa08a

invoice num_satoshis: 359

invoice route_hints: [hop_hints {
  node_id: "03a157fa253384f49df1343eb4d8ed20fb000dd04abb4f1a519306facb216fe3c3"
  chan_id: 17653461947383733890
  fee_base_msat: 1000
  fee_proportional_millionths: 1
  cltv_expiry_delta: 80
}
]

expected route: ['edward', 'dave', 'charlie', 'bob', 'alice']
actual channel capacities:
(✔) (A) cap: 1000000 sat, edward->[bal: 85400 sat|res: 10000 sat|spend: 70870 sat], dave->[bal: 911130 sat|res: 10000 sat|spend: 896600 sat], commit_fee: 2810
(✔) (A) cap: 1000000 sat, dave->[bal: 85500 sat|res: 10000 sat|spend: 70970 sat], charlie->[bal: 911030 sat|res: 10000 sat|spend: 896500 sat], commit_fee: 2810
(✔) (A) cap: 1000000 sat, charlie->[bal: 85600 sat|res: 10000 sat|spend: 71070 sat], bob->[bal: 910930 sat|res: 10000 sat|spend: 896400 sat], commit_fee: 2810
(✔) (A) cap: 100000 sat, bob->[bal: 50000 sat|res: 1062 sat|spend: 44408 sat], alice->[bal: 46920 sat|res: 1000 sat|spend: 41390 sat], commit_fee: 2420
(✔) (A) cap: 200000000 Asset1, bob->[bal: 3623500 Asset1], alice->[bal: 196376500 Asset1]

payment_hash: "24555b211a31d111c00c87ab8c4bdc646e1f43f0e217fec8706e399b4e7fa08a"
value: 359
creation_date: 1739767703
payment_preimage: "0000000000000000000000000000000000000000000000000000000000000000"
value_sat: 359
value_msat: 359310
payment_request: "lnbcrt3593100p1pnm90uhpp5y324kgg6x8g3rsqvs74ccj7uv3hp7slsugtlajrsdcueknnl5z9qdqqcqzzsxqyz5vqrzjqws40739xwz0f803xsltfk8dyrasqrwsf2a57xj3jvr04jepdl3u8a8akgd7mtk7sgqqqqlgqqqqqqgq2qsp55hqp6h75hhzum7psxdyc46xny9443skev0ls9hxm8yfpcmhx88us9qxpqysgqys8ukxksxmn6jrsulxqt83e3e4tde0ekjw8p2hartt0tq8xvtw6hrvmfwtaugyxvvpdytpz2r4uduv3jwuc3ed95dz2jqe9q8cu8gxqquv6vkq"
status: IN_FLIGHT
creation_time_ns: 1739767703973309540
payment_index: 1

payment_hash: "24555b211a31d111c00c87ab8c4bdc646e1f43f0e217fec8706e399b4e7fa08a"
value: 359
creation_date: 1739767703
payment_preimage: "0000000000000000000000000000000000000000000000000000000000000000"
value_sat: 359
value_msat: 359310
payment_request: "lnbcrt3593100p1pnm90uhpp5y324kgg6x8g3rsqvs74ccj7uv3hp7slsugtlajrsdcueknnl5z9qdqqcqzzsxqyz5vqrzjqws40739xwz0f803xsltfk8dyrasqrwsf2a57xj3jvr04jepdl3u8a8akgd7mtk7sgqqqqlgqqqqqqgq2qsp55hqp6h75hhzum7psxdyc46xny9443skev0ls9hxm8yfpcmhx88us9qxpqysgqys8ukxksxmn6jrsulxqt83e3e4tde0ekjw8p2hartt0tq8xvtw6hrvmfwtaugyxvvpdytpz2r4uduv3jwuc3ed95dz2jqe9q8cu8gxqquv6vkq"
status: FAILED
creation_time_ns: 1739767703973309540
payment_index: 1
failure_reason: FAILURE_REASON_NO_ROUTE

status: FAILED
failure_reason: FAILURE_REASON_NO_ROUTE

However, this problem happens randomly, I can't seem to get it in a repeatable way.

[ZZiigguurraatt]

Here's another example:

frank sending Asset1 via edward and bob receiving 360 of sats
MaxAllowableFee: 11
public channels frank knows about:
charlie(EEE) <---- 1000000 sat ----> dave(EEE)
edward(EEE) <---- 1000000 sat ----> dave(EEE)

r_hash: "w\257\331Pf*\023\333\334\223\002B\250\331<p\245q\313\342(z\003\0079\246\306\022=\235\255\330"
payment_request: "lnbcrt3600n1pnm948ypp5w7haj5rx9gfahhynqfp23kfuwzjhrjlz9paqxpee5mrpy0va4hvqdqqcqzzsxqyz5vqsp5d3qhp5lnr5dhwkajvwtl7ce5k9encm0f9uflt33tw927qynx2hvs9qxpqysgq93p24jtfywy6tcmfc678pfz957px47ezjs6x5tj2ymhkdcrwxwq9elwqrumxjm56pwz4nj3tpm2wxvpw4067dvqpa5t3rwkfx2f3x7cpr9f64p"
add_index: 1
payment_addr: "lAp\323\363\035\033w[\262c\227\377c4\261s<m\351/\023\365\306+qU\340\022fU\331"

r_hash: 77afd950662a13dbdc930242a8d93c70a571cbe2287a030739a6c6123d9dadd8

invoice asset_amount: 36539
invoice num_satoshis: 360

invoice route_hints: []

expected route: ['frank', 'edward', 'dave', 'charlie', 'bob']
actual channel capacities:
(✔) (A) cap: 100000 sat, frank->[bal: 50000 sat|res: 1062 sat|spend: 44408 sat], edward->[bal: 46920 sat|res: 1000 sat|spend: 41390 sat], commit_fee: 2420
(✔) (A) cap: 200000000 Asset1, frank->[bal: 461993 Asset1], edward->[bal: 199538007 Asset1]
(✔) (A) cap: 1000000 sat, edward->[bal: 54696 sat|res: 10000 sat|spend: 40166 sat], dave->[bal: 941833 sat|res: 10000 sat|spend: 927303 sat], commit_fee: 2811
(✔) (A) cap: 1000000 sat, dave->[bal: 54703 sat|res: 10000 sat|spend: 40173 sat], charlie->[bal: 941826 sat|res: 10000 sat|spend: 927296 sat], commit_fee: 2811
(✔) (A) cap: 1000000 sat, charlie->[bal: 54710 sat|res: 10000 sat|spend: 40180 sat], bob->[bal: 941819 sat|res: 10000 sat|spend: 927289 sat], commit_fee: 2811

accepted_sell_order {
  peer: "026598c032a4100f7e2d03b63c1a928094675c6a84aabef65a700832cda367a61f"
  id: "\303\034_\244\276\242J\236_\350H\241\202:\234\227\251\177-T\234;\306n\365^\251E\327\335k\003"
  scid: 17680755304542595843
  asset_amount: 36551
  bid_asset_rate {
    coefficient: "9852216748"
  }
  expiry: 1739773191
  min_transportable_msat: 354010
}

payment_result {
  payment_hash: "77afd950662a13dbdc930242a8d93c70a571cbe2287a030739a6c6123d9dadd8"
  value: 360
  creation_date: 1739773156
  payment_preimage: "0000000000000000000000000000000000000000000000000000000000000000"
  value_sat: 360
  value_msat: 360000
  payment_request: "lnbcrt3600n1pnm948ypp5w7haj5rx9gfahhynqfp23kfuwzjhrjlz9paqxpee5mrpy0va4hvqdqqcqzzsxqyz5vqsp5d3qhp5lnr5dhwkajvwtl7ce5k9encm0f9uflt33tw927qynx2hvs9qxpqysgq93p24jtfywy6tcmfc678pfz957px47ezjs6x5tj2ymhkdcrwxwq9elwqrumxjm56pwz4nj3tpm2wxvpw4067dvqpa5t3rwkfx2f3x7cpr9f64p"
  status: IN_FLIGHT
  creation_time_ns: 1739773156998230209
  payment_index: 8
  first_hop_custom_records {
    key: 65538
    value: "\303\034_\244\276\242J\236_\350H\241\202:\234\227\251\177-T\234;\306n\365^\251E\327\335k\003"
  }
}

payment_result {
  payment_hash: "77afd950662a13dbdc930242a8d93c70a571cbe2287a030739a6c6123d9dadd8"
  value: 360
  creation_date: 1739773156
  payment_preimage: "0000000000000000000000000000000000000000000000000000000000000000"
  value_sat: 360
  value_msat: 360000
  payment_request: "lnbcrt3600n1pnm948ypp5w7haj5rx9gfahhynqfp23kfuwzjhrjlz9paqxpee5mrpy0va4hvqdqqcqzzsxqyz5vqsp5d3qhp5lnr5dhwkajvwtl7ce5k9encm0f9uflt33tw927qynx2hvs9qxpqysgq93p24jtfywy6tcmfc678pfz957px47ezjs6x5tj2ymhkdcrwxwq9elwqrumxjm56pwz4nj3tpm2wxvpw4067dvqpa5t3rwkfx2f3x7cpr9f64p"
  status: FAILED
  creation_time_ns: 1739773156998230209
  payment_index: 8
  failure_reason: FAILURE_REASON_NO_ROUTE
  first_hop_custom_records {
    key: 65538
    value: "\303\034_\244\276\242J\236_\350H\241\202:\234\227\251\177-T\234;\306n\365^\251E\327\335k\003"
  }
}

status: FAILED
failure_reason: FAILURE_REASON_NO_ROUTE