Flickering Temp control pushbutton LEDs (archive)

I hope someone has had this problem and solved it!
Below the thumbwheels are the pushbuttons controlling the airflow (panel,auto,floor). They are lighted with LEDs behind the buttons (ask me how I know). When I start up the car at night, both the left and right sets of buttons are illuminated red so you can see which to push when it is dark. But after a minute, the left side starts flickering on and off for maybe a minute, and then goes off for good. The green LED's still work to indicate which button is pushed. All 3 red LEDs act in unison.

So I took the unit apart and then took the back off the pushbutton assembly (hard to reassemble!!!) I inspected the PC board with a good magnifier and could not find any poor solder joints or cracked traces. There are several diodes and resistors that may be involved in this conspiracy, but before blindly replacing whatever I can, I thought I should go to the mountain and ask one of you gurus that read all the way through this message. I would be afraid to ask the BMW dealer what a new control would cost. Are schematics available anywhere?
Thanks a lot, Steve
'94 740i
'79 528i

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