A30T - Repetier - Prusaslicer; stalled printing??

[rotormansa]

The framework is this:
A30T printer
Prusaslicer 2.3.0 for slicing a multi color print (two colors on same layer)
Repetier-Host & Repetier-Server as printer control

When printing from Repetier (host or slave) with gcode created by Prusaslicer, a long stall happens when swapping tools (filament) and printing via USB. Same gcode file put on the TF card and printed from the A30T front panel interface, there are no stalls.

Experiemented a little and found the "Communication Timeout" in Repetier was set for 40seconds. I changed this to 2 seconds and the stalling stopped. I did not see any errors on the ACK screen of Repetier. Can anyone explain?