PDF crashes on markup

Hello,

I work in construction and me as a part of the IT department am providing iPAD Pros to our staff on the construction side to make changes in plans.

For the past weeks we have been encountering a problem, where some plans are freezing for several minutes or crashing when opening and using the markup feature to make changes in them.

This problem does not exists with every plan, but with large ones (of whole complexes with many layers).

I narrowed the problem down to occuring after 14.8 or later

I tested it with an iPad Pro with iOS 14.4 and 14.8 and it worked just fine.

On the other hand I tried it with iPad Pro with 15.7 and newer and it doesn't work there.

Doesn't work on 16.2 with the M1/2 or an older Bionics Chip in case someone is wondering.

I tried the workaround with the books app and it is not an option, because the books app crashes already when opening the plan.

Maybe someone had the same problem at one point.

Thanks in advance.