Open AND create the pdf? What about just "open"? And what about just "create the pdf"?
Separating the 2 will help diagnose the issue.
How are you creating your PDF? PDF printer or file - save as?
Majority of the time is opening up the drawing and going to each sheet so Lets emphasize on that and not so much on the PDF.
I've personally never noticed a performance problem with repeat regions. The past few years my largest ones have been in the 50-75 component range.
Are you using a lot of repeat region relations? Maybe strip out anything that is not basic and see if that helps.
Or creating a "basic" repeat region with nothing other than index number and file-name or part number parameter and seeing if that is still slow.
a 10 sheet drawing with a significantly large repeat region is causing slow downs and random exit when the BOM is removed and the drw saved. This is an unusual behavior and time wasting.
Did you try and the dtl option update_solid all?
Does the issue happen with more recent release?
Finally if you can file a case and attach the traceback for analysis.