My builds started failing since updating to durable task plugin 1.18.  It would appear that the main script execution line was setting $LASTEXITCODE to 1 but $MAINSCRIPT was exiting with 0.

powershellHelper.ps1 line 53 is currently:

& { & $MainScript | Out-FileNoBom -Writer $OutputWriter } *>&1 | Out-FileNoBom -Writer $LogWriter;

And my take is that Out-FileNoBom can contribute to the $LASTEXITCODE, so the step can fail because of a logging error.  I found removing the $LogWriter or even the "*>&1" made it start working in a sandbox outside of Jenkins. I think that running $MainScript in isolation and capturing that $LASTEXITCODE, then doing the logging may be a more robust solution?

I've switched to using bat commands as a work around in the mean time.