Remember Liquid Paper? A.K.A. "WhiteOut"? Find an old bottle that hasn't dried up yet. Then mark a line between the nut and dropout, and ride 'til it loosens again. That might shed some light on how easily / how much it loosens.
You're taking note of the lever position when you re-tighten it, and the lever does not change position; right?
What material are the dropouts? Are the inside surfaces of the cam and nut "knurled", and do you see them marking / digging into the dropouts? Same question wrt. the outside surfaces of the locknuts.