Negative Lab Pro v3.1 - New Color Processing, Support for Slide Film, Improved Batch Editing, and More

EDIT: Just saw in the beta report section that it has to do with the LR version. Because my iMac is an old one from 2013 I try to stay as much on an old LR version as possible, so I can use the same catalogue on both machines…
guess I’ve either to stay at NLP 3.0.2 or upgrade my old iMac…

I just downloaded the beta 10 and installed it over the 3.0.2 and tried to re-convert some scans and also some new dngs.
However, it does not work and always stops with an error “bad argument #4 to ‘format’ (no value)”.
Any ideas what might be the problem?

I’m on a MacBook Air M1