Corrupt STL Export - NX Journaling

I have a complex part which resembles a kayak (attached), I have a python journalling script which changes some dimensions and suppresses/unsuppresses some features, then exports an STL of the part + JSON file with the parameters used.

When I manually export an STL it has no errors, but all of the STL files (3500 of them) which have been created by my code will not open - giving me Error Code: 0x80004005 from the default windows app. These files are also used in a web app, and they will not display their either. However, they appear to have a file size, so must contain something - I have managed to get it to work by running identical code (copy + paste) on the same master part file and it has opened with no issues.

Any ideas on how to fix this or what could have caused it? I need these files to work urgently, so many help is really appreciated.

I have attached a screenshot of the error code and a link to the GitHub repository for the code:

GITHUB

ErrorCode

I wanted to attach the master part file and STL too but I couldn't see how to. I am happy to provide any further information needed.

Thanks