Hi Bazza,
Thank you very much for the question and I am very sorry about the issue!
From the description, I believe this is a file-specific issue. Could you share with me the problematic file in PLA format, as well as a short video about the behavior? Please let me know if you need a secure place to upload the file!
Looking forward to hearing from you!
Best regards,
Minh
Minh Nguyen
Technical Support Engineer
GRAPHISOFT