Repairing Yashica Mat 123g

I purchased a Yashica mat 124g for the low price of $50 in a clearance section. Gorgeous exterior and case. However, obviously there are issues hence the low price.

1. Self-timer stuck due to being set while in the flash sync mode, easily repaired.

2. Crank lever and mechanism jammed (had similar issues with an older Yashica model rather often but eventually would function properly again.

3. Frame counter does not move despite the back closed and using a test roll of film (I always have a roll specifically for testing cameras).

4. Light meter is untested, that will follow after all other repairs are made.

I removed the cover for access to the crank and frame count mechanisms and on first glance everything is clean and lubricated. However, the spring for the mechanism to switch between 12ex and 24ex was shot and needed to be replaced. I keep spare springs on for such occasions. Spring replaced and tested for similar tension as the original and all is well.

After testing each function in order of correction functioning such as when the crank is moved into the shutter cocked position, the series of mechanisms to deploy the shutter followed by continuing to wind to advance to the next frame, the crank does become stuck which will not proper advancement of the film for the next exposure. When all mechanism do decide to work properly, the frame counter disc will not move on its own. After running over the mechanisms again I am able to spin the disc from empty to the first frame.

I have done quite a bit of research but have not found any solutions to this specific issue. Does anyone know what may be causing this?

I had to do a few minor repairs to my Mat 124 (like the G, but all metal) after I bought it. I found some of Rick Oleson's exploded drawings helpful. You can find an example here:

Basic TLR Repair Notes

Also, I googled "Yashica Mat repair" and got a lot of hits on how-to, including several YouTube videos. You might want to check these out.

A rather sad thread from 2001 about Yashica Mats but one poster thinks the cost (at that time) of repair is worth it

Yashica-Mat Repair?