vlan assignment to interfaces upon bulk edit clears previouslly assigned ones

[LuPo]

It is not uncommon to add vlans to interfaces which already have other vlans defined. At the moment all the vlans present on a tagged interface are being cleared and subsequently new vlan/s are being assigned.
In a possible scenario tagged interfaces are configured as follows:
1-5,11-15 : VLAN A
6-10,16-20 : VLAN B

On bulk edit interfaces 1-20 with intention to add VLAN C to the already defined vlans, the result is in having only VLAN C on interfaces 1-20

[LuPo]

it is actually a bug, I will open an issue