I think that there is a latch underneath the carriage to lock the carriage in place when it has been taken off the base.  This is to stop the carriage sliding from side-to-side and trapping your fingers.  For some reason, it might still be engaged with the carriage replaced on the base.  Take the carriage on and off and see if the latch is engaged in the escapement rack.  The latch should withdraw automatically as the carriage goes down on its base.

The latch is making good contact with its stationary mating surface on the lower part of the machine when I place and lock the carriage onto the machine.

My space-bar is jammed and the seller told me that the metal body member just below the space-bar took a hit at some point in time in the past and the carriage stopped moving then and the machine was just put away for years in their house.

In the next day or so I will remove the body panels and will re-form this section of metal in front of the space-bar so it becomes free to move.  Think this might be my problem.  My space bar is sort of trashed as well..so I have a "new" replacement space-bar to put back on the machine.

I will also re-felt the panels when I have them off and do a much deeper cleaning while the chassis is fully exposed.

Will post more as I have progress to report.

So I got a little closer to finding the cause of my problem with my new SG1.

I left the boy panels off for now, but put the carriage back onto the lower chassis with the 4 machine feet in place at the bottom of the chassis.

The machine stays in "line lock" full time and as long as I hit the M-R key after each key strike or space-bar strike, the carriage moves as it should.

In the photo, below, there is a mechanism with 2 small metal paddles that work in opposition.  The paddles make contact with plungers that come in/out in opposition of each other from the upper carriage.  I have shown those contact points in my photo with red dots.

The mechanism has some rust, so I have wrapped it with with small pieces of cotton rags and soaked the mechanism and rags in PB Blaster.

Will let that site for a day and them go further to see if the mechanism may need to gentle adjusting.

With my deep cleaning of the entire chassis, these other problems have gone away by just dissolving the hardened oil/grease and rust off of all the chassis parts.  No more :  1) sticky keys  2) Tab clear key now is free to move  3) shift and shift lock lever now return fully 100% to their up positions and the basket locks in place  4) both ribbon spools now turn/drive and the automatic reversal is now working.

Getting closer to a nice working machine !
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p.s. 

Tab functions all work and carriage moves freely.  Tabs can be set, can be cleared individually or with the all-clear levers on either side of the carriage.

Back-space key works and carriage moves back with the press of each key stroke.

Carriage just does not move when a type-key or the space bar is pressed.  Only moves when the M-R key is pressed before the other key or space bar is pressed afterwards.
 

Well thanks to "Chris" who runs the Olympia SG1 Typewriter Group over on FaceBook, my SG1 is now fully functional and ready to have its body panels put back into place.

Chris posted up the photo (see below) of a backwards-facing "7" shaped bracket that gets jammed sometimes in the shipping process of such a heavy machine.My little backwards-facing "7" lever was sprung/bound. Gentle coaxing with a slender flat-blade screwdriver freed it up and it went "boiiiinnng" when it popped back into place.

Put a new ribbon on and typed on a 28# piece of paper with my Avery plastic sheet behind it. I do not even need to make any shift-adjustments on the machine. The typed lines look so good. Brand new silk ribbon from RibbonsUnlimited.

Tomorrow I will put the body panels back into place.  And spend some more time with my machine to see if she needs any other adjustments or love.
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