If you level immediately after pulling in, you might loose a few pounds of tire pressure as well, and it may add to the problem. Sometimes you'll shift on gravel or dirt.
When my new unit gets here in a few weeks, I'll do things a little differently than on my current unit...right now, I level a little high on the slide side. I'm fond of using those large rear view levels so I don't have to keep getting out and checking (using Anderson levelers as well ). When I mount the level on the new trailer, I'm going to let it sit for a while, run the slides out, THEN level it. After that, I'm going to pull in the slides and mount the level. If it leans any from the slides, it should be accounted for.
2012 Chevy Tahoe LTZ - HD tow package
2017 Rockwood 2703WS Emerald Edition