Thanks for the information.
The only step you can take here is to try to factory reset the tv:
Press and hold volume down/- button on the side, along with MENU on the panasonic remote, together, for 5 seconds, until power shuts down.
Restart, and check for functionality. If the problem continues it would confirm an internal fault.
In the end, it really doesn't matter which of the issues it is though. This tv is so old that the firmware can't be updated (no updates available). A sensor/board could be replaced, but won't be cost effective to do so. The parts are no longer available anyway, and even when they can be found, labor costs alone would quickly exceed the value of the tv. You'd be in the $250 range for repairs, which just isn't worth it for an 8 year old 26" tv. The tv is already well past its 5 year service life, and could be replaced with a brand new LED tv with a fresh warranty for $150-200.
Depending how you’d like to proceed here, I can help with finding parts, finding a repair shop, or recommending replacement options. Just let me know..
Best regards, ***** ***** for the news,