You may want to check the continuity of the traces if you haven’t already done so. You are aware your set is a Japanese market model? Do you have the remote control? I see the remote sensor at the lower left. The American KVX 370 dose not have remote capability. Possible interaction with the remote might solve your problem if everything else checks out.
Andy is the guy. He repaired my two, 11 and 8 years ago. Still up and running.
If you don’t have the service and schematics, you can get them here for the KVX 370.
https://visions4netjournal.com/resources/
Hope all goes well.