Snapshot Pro - Almost always getting Internal Server Error

I keep getting an internal server error whenever I try to do a manual run of the backup. The automated runs don't seem to work either since I never see a result produced.

Here's what I've done:
1. Increased execution time to 90 seconds (from 30)
2. The memory is already at 512M and the Usage displayed seems to stay way below that.
3. Tried doing separate backups of just database tables and just files.
4. Tried looking at the produced logs but there does not seem to be any error messages.

What should I try next?
Screen grab is here: