the friend is absolutely right, the problem was in the 817B photo coupler and the TL431 regulator

TV repaired and working

I was very happy after I managed to repair the source plate, I had even closed the TV and showed a video of the TV working for the owner. When he arrived at the workshop, when I turned on the TV, I noticed that the channels changed by themselves, the volume indication also happened the same thing. I noticed that the integrated processor of the main board was a little hot, I ended up discouraged by the situation of the TV.

Try turning off the local TV keyboard and see if the channels are switched.
If the channels are switched, then look for a malfunction in the mainboard.

I even turned off the rear button on the TV, the one that switches channels and changes volume without success (still changing channels alone)

Could it be the problem SENK13 1337-CB PRM94200 (IC901) chip?

I'm hoping he isn't the problem.

The strange thing is that the TV was working perfectly until I took a photo and video to send to the owner of the TV.

Coincidence.
Check the entire circuit from the keyboard to the processor. Perhaps there is a malfunction somewhere. Many times I had capacitors, zener diodes and processor faulty in this circuit.