For some strange reason, resting on Solstheim doesn't restore either health, stamina or magicka. What's even stranger about it is that I can do it fine for a random amount of times when I load a fresh save where it hasn't occured yet, and then it just shuts off.

As in... I get off the boat. I rest 5 times, and on the 6th time, it wont regen anything. I reload the save but this time it only takes 3 tries before it stops working. This only happens on Solstheim however! I've got tons of mods, but I've turned off all of the ones affecting regen (well, the only one was Frostfall) and it hasn't changed anything, I'm afraid.

Is anyone familiar with this bug?

You don't regen when you sleep, or at least like you think. Regen happens all the time, so that you are usually healed up before you can even sleep.

This is a mod issue, so I will move it to that section.