There is a bug in the Camera App regarding the filenames used to save images captured with the Playbook's camera.
I reported it in the Playbook Forums 2.1 findings thread, but it will certainly get lost in the shuffle. So I'm posting here with a link to the descripton of the bug itself.
Yes. It won't overwrite existing files. It will, however, fill in the gaps in the file naming scheme caused by previously deleting pics. This is based on a sequence number in the filename of image and video files.
Did you ever use the Beta OS? Because I too experienced this issue, but it started back a while ago. I thought it was because I had Restored to another Playbook, but maybe not.