Annotation is glitchy.

I always annotate PDFs using Books but ever since the auto-shape function stopped working, I just annotate directly from when I open the document in Files. Just today, I noticed that Files will suddenly restart or reopen my document, and I find out that my annotations were not saved at all. This happens about 5 times in 30 minutes. What I have been doing is to tap 'Done' after a chunk of annotation to save my progress. At first I thought it was my pencil but it was working fine in Freeform. I also restarted my iPad but the same thing happens. Is there a current issue, or is there any other troubleshooting step I can try? Thanks.