This isn't a known bug, and I haven't seen this issue before in my experience either. If you'd like to share a sample IPB, I'd be more than happy to have our development team take a look at it to try to solve this issue. If so, you can email me directly at email@example.com
Thanks for getting back to me.
The problem is intermittent and only happens every other day. It seems it is not dependant on the file. When it happens again, I will send you the file.