Resolution:
If a pdriver script calls a batch file that uses the windows "start" command, it might cause a Windows engine to be Busy indefinitely.

The start command is an interactive command that sometimes generates a popup on the engine machine. If manual intervention is not done, the popup will wait indefinitely for user input, causing the engine to be Busy forever.

The workaround for this is to use taskMaxTime in the pdriver script or to simply not use the "start" command to execute batches.

Example batch file with start command: start "Testbusy %3" /B /LOW /WAIT "%1resourcesgridlibscripttest.exe"

Example batch file without start command: "%1resourcesgridlibscripttest.exe"