Hi there. It could be many things, obviously. And it sounds like you are dealing with mechanical and electrical issues. I would remove the decoder, fix the gear problem in dc mode, and after successfully doing that, install the decoder. The short is probably the result of your decoder installation.
Simon
Hi, I'm currently having an issue with a Roundhouse/MDC 2-truck Shay. I disassembled it to fix the gear, in the gearbox, that was loose on its axle, preventing it from moving the locomotive. I did this, and I installed a Soundtraxx TSU-1000 in the tender. I then powered up the shay on DCC, but the shay immediatley shorted out, creating a "cricket" sounding noise coming from the front truck. I assumed the electricity wasn't flowing, so I took off the truck, made sure everything was in place (everything was...), and put it back on. Then, I turned it on, and it shorted out again. This repeated a few times..
Any help with this issue will be highly appreciated, thanks.