Interestingly I had a similar issue. It was odd. I let the program run over night. It went from 8 hours remaining last night, to 4 days remaining this morning. I was moving my laptop (and external drive connected) upstairs to continue... After putting the laptop down I moved the external drive off of the keyboard - ad all of a sudden the progress bar started moving and then everything was complete and it said it found a whole bunch of files.
Showed a lot of files as recoverable, but after doing so (these are images) they cannot be opened. Im assuming that this is probably related to that scenario where 0000s are in the header. I have not done anything to validate this yet.