similarly, I go through the leveling, do a viewing/imaging session and then shut down the Seestar. Leave it exactly where it was (don't move it at all). Next time I turn it on, check the level, and it says it's out of level? How can it not be level when it's still exactly where it was when I leveled it previously? And yes, I've done the level calibration.
I've also learned to do the compass calibration before leveling. Even though I do the compass calibration by simply loosening the bolt on my mount and just spinning the Seestar without moving the mount itself at all. Whenever I level first before compass calibration, whenever I finish the compass calibration, the Seestar says it out of level again.