I also don't know for sure the answer, but at least I have a more logical supposition. The camera has coil under the bottom plate that is basically an electromagnet to control shutter speeds. It has a very thin wire that lets power flow to it. However, that wire has only a thin insulation and it might short circuit at some point. If that is the case, is not complicated to fix, but it requires precision. A workaround would be to only let battery while shooting. 5 mins, or even 10 maybe won't drain the battery; at least it makes the camera usable