I don’t think so. I also get the not found error when trying to call lstat like that, but the file watcher works fine regardless.
This may be some kind of a permission issue. The only thing that I can think about right now is that the /sdcard/Camera/DCIM folder seems to exist in Android by default from the very first boot, while the /sdcard/Pictures/Screenshots folder gets created only when you actually take the first screenshot.
Some screenshots of the Syncthing Web GUI from both sides would probably help. You should also check the log files, especially on Android, to see if there are any errors recorded there. See https://forum.syncthing.net/t/only-non-pdf-files-are-getting-deleted/16408/16 for how to get the logs on Android.