I think I have the same problem in this link. Narrow range and high octave.viewtopic.php?f=12&t=25652
100A 100B is 500 ohms, R106 is 24K , TM5 is 1.7k (it is a 5k trimpot)
Today, the x0xb0x has the note drifted and out of tune like crazy. I record a new DC voltage reading. I have written them in light blue text. It is only one of the reading. Sometimes the reading is different on those blue text area.
I have already re-touch all soldering point with the soldering pen to make sure they have a good contact, but it doesn't fix anything. I think must be one of the component has problem.