I read your pm in my email earlier and come on to answer you and saw your thread here so thought I'd reply here instead.
I believe your 4920 is the same basically as my 4900.
The lift cylinders are double acting. Often unbalanced side to side flotation spring tension will cause the header to lift unevenly, however sounds like you may have a cylinder issue at minimum possibly.
Reason for the double acting system on header lift, is so you can collapse the cylinders with the table on the ground and it causes the table to actually roll backwards and up towards the windshield, and this gives you additional negative guard angle for picking up down grain. Float isn't as responsive in this position and when things set right, you can just skate the tips of the guards above the ground when needed. To get back to normal settings, you lift the table just enough where you can see it roll back forward and the rear of table will drop back down.
As for the issue with the switches, yes you need to hold the switch to drop table. Mine used to lock for lifting, however when the switch cratered, I replaced it with one that don't lock as I found that very annoying when making adjustments while cutting. Reel needs to be held both ways. Sounds like you have an issue with power getting crossed over between your switches and your solenoids which activate the valves. If everything is not exactly right with those solenoids they will cause the spools to hang up, often the worst offender is the table clutch. Biggest thing that messes them up is if you over tighten them.
Just had a idea here, if you don't have a book, go to the Macdon site, you should be able to download the exact books for you machine and table, owners and parts.
Edit, well I see you posted again while I was typing lol, well looks like you got some of it figured out, good luck
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