hi bergsj, "i always check a level from both sides, then switch ends, for plumb and level, before i buy one. it seems one in 5 is actually "on" in all permutations" I never trust a level I haven't checked myself, with a plumb bob,water level or laser. maybe your wall, is out of square a bit? which will throw studs out of plumb. a few things I've learned in my years of construction #1- never assume anything is square! before you check it. #2- gravity, pulls straight down, if you tie a string to a rock, and let it hang, the string will bring itself to plumb.#3- water will run level when unobstructed, put water in a glass, no matter how you hold the glass the water will go to level if no bubbles.
I meant to post on your thread for framing basement walls help, but life and Christmas got in the way. wanted to suggest you make sure your basement is square, before you began your walls. so can line the soffit up square. sounds a bit late now? though walls can be moved if needed? depending on your choice of ceilings in the basement? depends on how square the soffit is to walls? drywall ceilings can hide a lot. drop ceilings with any kind of pattern? not so much. the smaller the pattern, the more need for squareness! if need any help with that? let me know!
other than that, good luck with your basement remodel