Not crashing from the 6-10 is probably because you healed normally from just resting.
I don't think a misplaced string would be the cause, if it was, you would just see some weird text in place of the healing one, not a crash.
Well, the crappy way to figure it out would be to do a brand new install, and install the mods one at a time, checking after each install to make sure that you can rest fine. When it crashes, you know that the last mod you installed caused the problem.
Also, make sure to check to make sure it doesn't crash before you install anything, and once you have found the mod that crashes the game, do a clean install again, and install that mod by itself. This is to make sure that its not a conflict with another mod that's causing the crash.
The cuplrit might be Dark Ritual, I know that I had some problems with that mod, but it's been so long since I installed it that I don't remember what the issue was.