Kobo Glo not properly saving position (2.3.1)

Having a bit of a problem with my Glo. Every time I leave a non-Kepub ebook it doesn't reopen on the right page. Depending on the book it can jump back by anything from one to five pages. If you leave and then reopen the book multiple times it will keep skipping backwards until it hits the beginning of the chapter. I did a factory reset to see if that would sort it but unfortunately it made no difference.

This bug has only popped up since I updated to 2.3.1. Anyone else seeing this? Any ideas what might be causing it?

Thanks.