Dear Piotr,
Thank you very much for sharing the issue and I am very sorry about the experience!
After some discussion, it looks like a defect to us, although it is not clear what is causing it at the moment. Is it possible for you to share the file (in PLA format) for further investigation? Please let me know if you will need a secure place to upload the file also.
Looking forward to hearing from you!
Best regards,
Minh
Minh Nguyen
Technical Support Engineer
GRAPHISOFT