These early revision scopes are known for their leaky caps (I just fixed a 'non-letter' model the other week actually, and I had to make a new VCO board too due to corrosion, it's the little tiny board hanging off the ACQ board).
It had weird errors and it all came up perfect with the new caps.
I usually remove all the old caps by giving them a wiggle until they snap off, then clean up the pads with a solder sucker,
lots of flux, isopropyl alcohol and patience.
Then I throw the boards as they are through the dishwasher to clean off the capacitor drippings etc, and then once they have perfectly dried after a couple days and a hairdryer, I finally solder in all the new caps.
If you need a replacement VCO board due to corrosion damage, I can send you a spare for the cost of a letter from Japan (won't cost much).
Here's a link to the video.of the repair:
https://youtu.be/3LS_Xg1ysXk