Standard Library Error Mocha Pro 2019.5

Hi:
I am Using Mocha Pro 2019.5 v 6.1.3-32 on AVID MC 8.8.1

I am using the remove module for a mic removal.
I am rotoing out foreground hand movement and replacing the mic on the man’s shirt.
The replace is working well, except for a few frames in the roto area where I get the “Standard Library Error”.
This behavior only began after I added an additional clean-plate for later in the scene. Prior to adding the clean-plate, this area of the roto was removing the mic with no problem.
Is there a limit to the number of cleanplates that can be used on a scene? Not sure what is causing the issue, I’ve rebooted and also updated from v6.1.1
Thanks,
Ed