When to use Select Window

[FMDuck]

Does anyone know specifically when GTRRs fail and when you need a Select Window script step?

I have a FM7 Multi-file solution that seems to fail to go to the proper layout/TO when doing a GTRR from a different file. It seems that it fails when the related file is first used because I regularly end up with unusual records in the table that's associated with the first layout.

Guesses are welcome (please let me know if your response is a guess though!)

Thanks much.