POST on the HTTP server is probably truncated #375

I'm retrieving the akumuli database entries with the "join" string via curl:

curl -v --data @$request http://localhost:8181/api/query
The $request is file containing this text:
{
"join": [ "gpu.util_M", "gpu.util_G","gpu.clock_G", "gpu.clock_M", "gpu.temp", "gpu.power", "gpu.SM_Active[%]", "gpu.SM_Occup[%]", "gpu.GR_Active[%]", "gpu.DRAM_Active[%]", "gpu.fp64[%]", "gpu.fp32[%]", "gpu.fp16[%]", "gpu.tensor[%]", "gpu.PCIE_RX[MB/s]", "gpu.PCIE_TX[MB/s]", "gpu.NVLINK_RX[MB/s]", "gpu.NVLINK_TX[MB/s]"],
"range": {
"from": "20200828T010000", "to": "20200922T140000"
},
"where" : { "ngpu": 4
},
"order-by": "time",
"limit": 10000000,
"output": { "format" : "csv", "timestamp" : "raw" }
}

This inquiry can be found in the akumuli.log associated to the curl retrieve event:
2020-09-23 15:11:22,347 [0x7ffe9fffc700] resp-protocol-parser [INFO] Starting protocol parser
2020-09-23 15:11:22,356 [0x7ffab17f9700] Main [ERROR] Query plan errornot found

and I get also the "-not found" error message in the output.

However, if I split the "join" string in two parts:

1. "gpu.util_M", "gpu.util_G","gpu.clock_G", "gpu.clock_M", "gpu.temp", "gpu.power"
2. all the rest
   I do get the output for each of these parts separately and no error is indicated.
   Remark - adding even a single additional entry to the (2) "join" string leads to an error.
   It buffles me since few months ago on a smaller database I could push the complete "join" inquiry without an error.

I guess the input buffer on the HTTP server is overflowing or some other error is occurring.
Please, advice.