Hanging mirrors seem to be a problem with these old M42 mount cameras. That is why my Spotmatic is in the shop.
I have an Electro X, too. The mirror lock up is inactive, but it is otherwise mint, and came with new seals. Someone seems to have solved the hanging mirror condition on mine by removing the foam at the top of the mirror box, probably when the seals were replaced. I do not know how good for it that is. So I will probably send that in for a CLA next.
One of my TL Supers is behaving itself, and was in surprisingly good condition considering how much I paid for it. It was practically in mint condition. The other I got for parts and is pretty much useless.
Although I cannot compare them side by side, I think that the TL Super is at least equal to my Spotmatic in every way. Compared side by side with my Electro X, I cannot really pick out a difference between the two. It makes me wonder why they bothered putting the electronically controlled shutter in it, since it does not seem to do anything other than make it slightly bigger.
Then again, most M42 mount cameras seem to be well built, their lenses are mostly compatible with each other, and you can build quite a collection of them across a relatively broad spectrum of manufacturers. One could speculate that interest in M42 mount cameras is an early indicator of a predisposition to GAS, just like spending endless hours searching the internet for information on LTM cameras seems to be 😉 😀
Richie