Yaesu FT-902DM ALC problem

In the middle of a faultfinding session and thought I'd share my problem with the fine minds out there. Got an FT-902DM on my bench. Problem is low power output on SSB of approx 50W. CW mode is fine at 100W+. The ALC kicks in way to early on USB or LSB, restricting the power. No ALC indication in CW mode - normal?

Thoughts:
1) In USB or LSB the SG supply voltage might be low indicating a supply voltage switching problem between SSB, CW and FM, AM modes. Will test this tomorrow.

2) I can't find the ALC adjustment. Spent ages looking for it, maybe there isn't one and power is regulated by (1). Could the ALC voltage be too much due to a resistor going high in the final?

3) Mode switch appears to have taken a knock. Perhaps a switch on it has been damaged, resulting in incorrect SG supply voltage selection?

Its not (1) or (3). SG is ~215V on CW, LSB, USB and 165V on FM,AM,FSK.

Fault has cleared itself after partially removing and checking mode switch. (Measured SG AFTER doing so.) Cleaned and pushed all the contacts down a bit so they had a better contact. Perhaps impact to mode switch displaced a contact slightly. Fault did not seem to be intermittent when mode switch was waggled though... hmmmm. Got a feeling I haven't seen the last of the problem.

I have the service manual for the 90x series. Let me poke around a bit and see what I can deduce.

(Also have two FT-901DMs at the moment so I could check condx as required.)

Problem has not returned :)
Been through the diagrams and can't confirm the exact failure mode. A bad contact for SG would have dissipated a fair amount of heat in the switch for what I was seeing plus it would have been mechanically sensitive. Hopefully it won't return..
Thanks for the offer of help.