Oh, I forget people still try to use AltAz for imaging. You have my sympathies for the troubles endured.

I didn't have the focus tube screws locked tight enough. I walked away from my rig for the comforts of my bed while the gear worked through the night. When I returned to the rig, I found that due to the way the rig was rotated in/on the mount ended with the camera directly ontop of the optical tube. Since the screws were not tight enough, the weight of the camera pushed the focus tubes into their most compact state. This clearly blew focus on all of the images from when ever it started to move. I have some lovely out of focus shots of a total eclipse for sale if you're interested ;-)

After that, I learned to manualy rotate my rig through the motion it will undertake through out the night in advance so that the camera is not side slung with the weight never to come straight down like that. I also try to arrange it so that it is always adding tension to the weight so that it is not pulling against the motion.