I know Eric is like a god here, and I recommended him to you. At the same time, do a low-cost test roll when the camera returns. He recently worked on a couple of my cameras and the ME Super came back with the same shutter problem that caused me to send it to him in the first place, a problem similar to yours. And the flash sync on the MX is still flawed, with a sliver of shutter curtain showing in the frame.
He's honest, stands behind his work, and I believe that he has earned his reputation through quality service again and again. Still, he's human and is dealing with complex little machines with lots of unique ways to go wrong. And some of those ways can't be diagnosed on a test bench, only in actual use. So run through the shutter speeds and check flash sync when the camera returns.
Your advantage is that I get the sense that he likes the LX. I also get the sense that he'd be fine never working on an MX again
More than anything, I think that parts for the MX are getting pretty rare. If he had the parts, I think he'd be happy just swapping out whatever subsystem creates the problems with my MX.
The ME Super that he repaired is working very well. Since I never used the flash on the MX, it's only an issue if I go to sell, and Eric has made it clear that he will do another round of work on the MX if I want. Just my luck to have two cameras that fall to the outer edges of the curve...