Solved Z axis problems

I was hoping some of you seasoned users can help me out- really frustrated.
Using my Robo-3D R1+
Matter Control 5.1

I have printed a part that I've used many times on this machine. Suddenly it wouldn't print properly this week. No recent upgrades. No work on printer.

I have it set up with auto level G29 , and normally it has worked ok, but suddenly it got wonky on me. Every time I tried to print even a calibration circle, the print head would hover above the glass about 1/2".

Tried turning everything off, rebooted my laptop, restarted Matter Control, turned on printer. No matter what I do, during the 9 point auto level sequence, it center points fine to the bed, then goes to the first front point (left side of the bed) and raises up on Z axis 1/2", then goes to the middle point and touches bed, same with the right front side, then it goes to the left middle point and raises up 1/2" Above bed, then touches down middle and right, then back up high on back left, and touches down middle and right.

I've checked to make sure the limit switches are seated properly, wires connected. I've tried manually leveling, but checked auto level before printing, just to have it revert back to above.

When I home it, X=0, Y=0, Z=5.40
I cant get home to reset even when I manually bring down Z-axis
I also tried entering -5.40 in z axis of eeprom. That didnt work either.

What am I missing???

 

I did that first thing. Wires are connected, nothing in the way of movement. Nuts are properly seated and limit switches are properly positioned under the brackets.

 

I found the problem that I have not seen addressed yet! I took the printer apart to check all connections/parts. After closer inspection I saw that the z axis threaded rod on ONE side was loose in the coupler! I could not tighten it up, so I removed it and saw they had wrapped it with friction tape at factory, which had come off. I wrapped it with fresh layer of tape- reassembled it and it tightened up perfectly. I manually adjusted the z axis on both sides to touch glass before turning printer on and starting software. It is now printing fine...
It makes sense since the two z axis motors turn in synch - if one is slipping, registration gets off.
Hope this helps someone else.

 

Wow- I thought the box it came in said it was an R1+, but its been awhile. My bad. Thx.