Since about May of this year one of my JVC SVHS machines has been out of service (SR-MV50). It would just boot into a black screen (it normally just has a blue screen output for VHS) with nothing else. The TV would detect a signal but it was just black. I later figured out it was wrongly booting into dubbing mode (which is used for dubbing to the DVD), and I was able to get it to play a VHS on a TV. Only problem was no audio for some reason which is a deal breaker. The physical DVD light, and the Dub light also did not function when they should have. The VHS and TBC lights worked.

Something that I remember when I opened the machine in May was that I saw a very small spiderweb. I was not able to find any bug bodies, but spiders are small and can find tight spaces to live/die in, potentially connecting circuits that were never designed to connect. So as a last ditch effort I threw the entire machine in a food dehydrator and set it to 150F for 3hrs. After letting it cool for 1hr I gave it a go. And it worked perfectly after it was done booting, with a Blue TV image and Stereo audio from the start.

I still don't know for certain what happened but it was probably literally a "bug".