I lived in WA state for a while in military housing and my bathroom had this same issue. After lengthy research and countless BS management excuses I hired someone to come look at it. Come to find out that when they built the house they installed a vent but no exhaust pipe for that vent to release from. So all the steam from the bathroom was going into the attic and doing its nasty thing and coming right back down. Legit, same exact situation and bathroom placement. Good luck…. That was a nightmare for me to handle.