This may not be a popular answer, but based on my limited experience with Fab 5.x (I had similar problems with a few discs) & a number of posts on this forum, I am continuing to use DVD Fab 4.120. I use it along with Any DVD, so new copy protections are not an issue.
My personal take is that Fab 5.x continues to be buggy.
I see only 3 feature advantages to 5 over 4:
The custom splitting options. I would like to use this feature
New copy protections (see above for my current solution)
Mobile options. I NEVER use this, I ONLY play dvd’s so I don’t care.
The moment I see a consensus on this forum that there is a largely bug free version of 5.x I will definitely try it again. My take is that we’re not there yet.
BTW, to the OP, I believe most if not all of the coasters I burned were from using the “Custom Split” option. Has that been the case with your issue?