Onkyo TX-NR717 erratic behaviour, AVR won't stay on

[wookiee]

I have Onkyo TX-NR717 that started exhibiting rather erratic behaviour. It started to turn off at random and surprisingly come on again by itself – no remote or button input. At first it was just an annoyance but with time this behaviour was impossible to ignore as it became more frequent. The unit is about 13 years old.
Service manual is attached.
I opened the unit and took out the power supply board BAPS-1145. I checked that standby transformer coils have continuity 1-3, 5-6, 8-9 and 11-12 are ok. There are no visible signs of overheating, no capacitors are bulging. I checked capacitors on BAPS-1145 with ESR meter, all have proper values and low ESR matching the reference tables. After taking apart, the unit would not come on at all. Pressing the power button had no effect. I hooked up scope to pins 6 and 7 on JL9000A on BAPS-1145 and here is the result after pressing the power button. These are MPOWER and STPOWER signals. I can’t remember which one is which on the attached plot.
 
So the signals MPOWER and STPOWER appeared momentarily and the unit stayed off. I decided to attempt to switch on the main transformer by applying 9V to pins 2,3 of the relay RL9101 to see what happens. When I did that, the unit turned on and stayed on even after removing the 9V from pins 2,3 of the relay RL9101. The unit stayed on until auto off (no input), I think it was after 30 mins of so.
The interesting thing is that now the unit appears to operate (almost) normally. When I press the power button, MPOWER and STPOWER appear and stay up and the unit turns on. However there is more strange behaviour. It appears that function keys on the front panel have a been assigned wrong functions. What I mean is that to change to a desired source you need to press a button to the right of actual label. If you have labels TUNER, TV/CD, PHONO, you need to press TV/CD to get TUNER and you need to press PHONO to get TV/CD.
Any ideas what is going on and what to look for?

[m k]

MPOWER is directly from the MCU, so from its point of view something unusual happened.
Maybe it changed to its default state, that is different from what it should be.