Beseler Dichro 45 set up questions

I managed to get my "new" Dichro 45 (non-S) running this afternoon.
Initially I couldn't get it to power up but after a review of a thread about similar problems here on APUG I "field stripped the electronics, reassembled it and got it to light up and work.
A couple of questions though. When I dial the filtration all the way out I still notice a slight change in illumination when I use the "Filter Out" lever on the bottom of the head.
I may need to do a little adjustment/lubrication of the cams and gears but want to ask about it first.

Also the chassis is a 45 MX II. Pretty good shape, a little the worse for wear from storage but not hideous, haven't really checked the alignment yet, that's on for tomorrow I hope. While playing around with the power up/down I managed to find out that it is possible to run the thing off the rails going down. (oops)
Should there be some kind of mechanical stop to prevent that from happening

Re running off the rails. There should be stud near the bottom and one more near the top on the right side frame. These contact the motor switch and force it to the off center position. If they are missing you can go beyond the end and off the rails. You could replace them with a small bolt if needed. There should be a threaded hole if the are missing.

Yes, at the bottom of the travel there should be a peg just like at the top.

That's kind of what I was guessing. Thanks