I do not replace those. Based on the experience of other technicians and my own, they don't seem necessary. I sent you a message on reddit if you want to chat more about the LX.

Yeah, my first guess for this kind of issue was also a bad switch contact. While this can sometimes be the source, it's more often a fault in the main PCB. A component failure. The only way I've heard of resolving it is by replacing the entire main PCB. But I'm hopeful that we will eventually learn more about the design of the main PCB and be able to identify exactly which component is responsible for the failure. It would be much easier to replace a bad capacitor than to source an entire PCB.

There is an STL file available on the main camera page, which you can send to an online 3D printing service. I would recommend using a lost wax brass casting process. Companies like Shapeways can do this for relatively cheap.

Yeah, this can sometimes get sticky. I recommend disassembly and cleaning before adding lubrication as that will get rid of the old sticky grease, which is usually enough to get it running smoothly. Follow the Mirror Box Guide until you have the lens mount separated from the mirror box. From here you can disassemble and clean the aperture coupling ring (there is no guide but it should be pretty simple to figure out). Use isopropyl alcohol to clean off the old grease. This is also a good time to inspect and/or clean the contacts for the aperture resistor. Reassemble the coupling ring and see if it moves smoothly. I usually leave the interface dry with no additional lubrication, but if it needs help you can add a light film of moly grease to the ring and the surfaces it contacts. Again, it should just be a light film of grease, not a thick layer as if you're packing ball bearings.

It can sometimes take a couple of attempts during reassembly to get everything working properly. Make sure to review all of the installation notes in the guide and to check as much functionality as possible after each piece goes back in. If you want more details about the mirror box, check out the mirror mechanism guide. It has a video showing the mechanism in action. If the shutter button is not working after reassembly, the mirror box is a good place to start investigating. That is what the shutter button fires first. Then the mirror triggers the shutter release.

Thanks for the advice on the weather sealing. I've only heard of one shop being able to replace the seals but I've wanted to experiment with some "home remedies".

In your other comment you mentioned having some bodies with the always on failure. I'd like to ask you some questions about them but iFixit doesn't have direct messaging. Are you online at any other forums where I could contact you? I'm on pentaxforums, photrio, and reddit mostly.

Yeah, I agree. It sounds like the "decrease" button is stuck. Since you already investigated the button itself, I would look into the contact between the top cover and the body. The decrease button communicates to the camera through the middle of those three contacts. If that contact is shorted to ground, it will act like it is stuck down.

I would check out the replacement guide for the ZX-5n. The construction of that camera is more similar to the MZ-30. Some of the wiring will be different but just take some pics for reference when reassembling. The parts page has a link to a place where you can order the gear or you can use the gear specs to search for parts on eBay and Aliexpress.

Pentax ZX-5n Mirror Motor Gear Replacement

It's hard to say precisely what the issue is but my guess is something around the aperture set lever. Unfortunately, I think you have to take it all apart and put it back together. Sometimes you just miss something. I would double check steps 32 and 33 and make sure those are followed during reassembly. You can also check out this video for a more in depth description of how the aperture mechanism is supposed to work. It might point you towards a more specific area.

https://www.youtube.com/watch?v=4V3x1cm-...

My first thought is to make sure you are testing the speeds with film in the camera, although this can be a bit tricky with some testers. For the slow speeds, like 1s, the camera measures the light off the surface of the film and calculates the proper exposure in real time. Without film loaded, it measures the light off the pressure plate or whatever you testing unit puts in the film plane. These are usually "darker" than film and result in artificially long shutter times.