I have same issue with ReadyNAS PRO 4.2.20 firmware and then installed LMS 7.7.2.
There are some .cue or .m3u playlist files that can cause crash of scanning process. LMS Server sometimes restarts (can be found in scanner.log or server.log files - select 1000 lines link under scan progress status page in LMS Settings/Information tab). I removed these "problem" files which where flagging issues in the log files. Then scan process continued again, but crashed when handling deleted items of the files removed, so had to relaunch full scan to get further. This took a couple of iterations.
Then hit some more issues with .WMA & .MP3 problem files (tags malformed, etc.) this caused again the scan process to aboard or let the LMS crash again.
Again removing the dirty audio files kicked the scan process a bit further.
At some moment the scan process is halted and nothing can be seen in the log files. You then have to aboard the scan process 'manually' to see which audio file caused the problem in log files.
Sometimes the scan process does crash, but does not return any details in log file. Sometimes you can see which was the last known scanned audio file or you have to look at the progress to find the last good audio file shown in LMS Web Settings interface. As the scan is performed in alphabetic order, you then have to find the correctly scanned audio file. This can be done to search for audio files that are coming after/below the last known well-scanned audio file. You have to iterate a couple of times to find the last know scanned audio file. I then removed the next couple of audio files and this resolved scan crash problem.
I still haven't gotten to the end of my music collection, but I hope to get there soon in one of these weekends
It seems that there is no proper routine in the scan process that handles error exceptions well enough (wrong formatted files, wrong tags, playlist interpreter limitations, etc.).
I guess Logitech still has some patching to do on this one...