Just got off the phone
with Edson and thought I'd pass along what I learned. They were refreshingly helpful and a pleasure to deal with.
The control shafts pass through delrin bushings. Those bushings occasionally swell up and bind the shafts as they pass through the housing. No amount of oil will help. The bushings have to be replaced.
The 2 phillips screws are retaining screws that fit in a slot on the control shafts. If there is a friction screw, it's a hex head
on just the throttle side.
They also recommended, while everything is apart and access is easier, to inspect the bracket that holds the cable housings. If it is nylon, it could age and break, rendering the cables