I ran into some issues trying to sync yesterday to my phone, as there were lots of "access denied" errors when trying to copy certain albums. As it turns out, the SD card was full (and hence Android wouldn't let the app add new files, as there was no space), but this wasn't at all obvious because of the weird access denied messages, and I wasted quite a while trying to fix until I realised what was wrong.
When syncs fail / errors happen, could a check happen to make sure it isn't the storage device being full causing the fail? Alternatively, maybe always show how full the storage device has become at the start/end of every sync, with an additional warning if it's full. Would help to diagnose silly (but not obvious) issues like this one. Thanks!