W2O8TC

I don't know why this is happening so I hope someone can help me. I am getting ready to put my winter rims/tires on the car soon so I decided to take my rims w/winter tires already mounted out of the storage and what do you know? Two of my tires lost pressure almost going flat.
Samething happened last winter except it was two front tires and this time, its one front and one rear. Tire shop guy at NTB put some kinda glue last winter on front two and I went through last winter without losing pressure and here I am, took the wheels out of the storage and two wheels lost pressure, almost gone flat. Does anyone have any idea why its going flat during the storage?? I took these winter rims off my car this spring with no problems. Anyone?????

Luke@tirerack

all tires loose pressure over time but to go from fully inflated to almost flat in approximately 8 months is more than normal pressure loss (which is about 1 PSI per month)

I would suspect a leaky valve stem