For another purpose, I made a .pdf with text annotations from various programs (foxit, xodo, etc),
to see how compatible annotations are across programs.
After adding it to paperpile and opening in the Android app, the android app crashed and could not be reopened without crashing again. I deleted the file from paperpile (web) and re-installed the Android app, this fixed the crashes.
It’s not possible to attach the .pdf here so I will email it separately.
This is not really a problem for me, however it might be a problem for someone. More generally, the thing I value most about paperpile is that it does not “lock us in” to using it via proprietary storage or database; supporting other people’s annotations would be a small part of this.