Critical USB printing bug back in v1.2.6: "Error:Line Number is not Last Line Number+1"

[mrcg]

Because of issue #186 i have installed v1.2.6 again.
Unfortunately the dual print failed again because of old bug #86 which was fixed with v1.2.0 but now it seems to be back again.

Dual print is sporadically failing with "Error:Line Number is not Last Line Number+1" when printing via USB (Octoprint on Raspberry).

Printing via USB becomes a nightmare. :-(

Based on terminal feedback from the Sigma controller two digits from the line number are missing:
Recv: Error:Line Number is not Last Line Number+1, Last Line: 188027
Recv: Resend: or:Line Number is not Last Line Number+1, Last Line: 8027

Error log from today:

Recv: ok
Send: N188018 G1 E-4.0000 F240034
Recv: ok
Send: N188019 G1 Z34.700 F100216
Recv: ok
Send: N188020 G1 X112.201 Y180.443 F1200068
Recv: ok
Send: N188021 G1 Z34.600 F100226
Recv: ok
Send: N188022 G1 E0.0000 F24002
Recv: ok
Send: N188023 G92 E0119
Recv: ok
Send: N188024 G1 X111.943 Y180.701 E0.0048 F360010
Recv: ok
Send: N188025 G1 X111.377 Y180.701 E0.0122104
Recv: ok
Send: N188026 G1 X112.201 Y179.877 E0.027698
Recv: ok
Send: N188027 G1 X112.201 Y179.312 E0.0350110
Recv: ok
Send: N188028 G1 X110.812 Y180.701 E0.0609*98
Recv: Error:Line Number is not Last Line Number+1, Last Line: 188027
Recv: Resend: or:Line Number is not Last Line Number+1, Last Line: 8027
Printer requested line 1 but no sufficient history is available, can't resend
Changing monitoring state from 'Printing' to 'Error: Printer requested line 1 but no sufficient history is available, can't resend'
Recv: send: 188028
Recv: ok

[willtmakinen78]

Same problem, however it is with Repetier Server at startup. I can't ever even get to the point of basic movements, as the printer never becomes properly connected. It happens at the sendin gof the first line, N1 M110.