Error "Unable to pack the files" while running slPacker.Pack in TestComplete 15.57

Hello,

I'm experiencing a problem with TestComplete 15.57 on a previously working code that uses the slPacker.Pack() function.

The latter now generates an "Unable to pack the files" error without adding any details to the error, so I have no idea where to look.
I've checked the parameters passed, which are correct.

Does anyone have the same symptom?
Any ideas?

Thanks in advance