So I've said this before, but I'm printing ABS.
I built an enclosure out of cardboard that seals REALLY well (let's just say my mechanical engineer GF went a bit overboard on the "engineering" of this box, so seals really well)
Ambient reaches 50℃ inside the box (I have a thermocouple inside the box).
Almost all of the bolts on my Ender 3 started going loose over time.
I've bought new lock-nuts and replaced every single lock-nut.
I also added thread-locker (blue/medium strength) on each of the nuts (then let it cure for 24 hours)
This actually seems to hold up to the heat and haven't had it come loose again.
It is amazing to me how everything just started going undone by the heat.
Thought maybe others would find this useful in the future if you are having the same problem (I tried at first just replacing the lock-nuts, they came loose again, so I think thread locker did it)