I've had a few people report that ffmpeg occasionally hangs on certain recordings. Seems to be consistently the same recordings, but not 'all' recordings.
Since you're already looking at the log file, could you grab a snippet that shows the problem? That might prove helpful.
There's not a lot TabloRipper can do, but it could timeout the ffmpeg session when it hangs. Unfortunately that'd result in a partial/incomplete rip. So I'm looking for feedback - what would you like to see happen (short of me magically fixing ffmpeg)?
As always, I recommend installing the latest versions of TabloRipper (you're already there) and ffmpeg. Can't hurt. Might help!
PS: Does the recording that hangs play correctly on your Tablo?