The problem with the tuneable IF/RF transformer "cans" is not the moisture, but the corrosion damage it leaves behind. There's a dirty trick inside many of them. A built-in capacitor serves to tune the coil inside to a range of frequencies. The cap isn't the dirty trick, but the way the capacitor is fabricated. A tiny hollow cylinder of ceramic has a metal coating applied in a vacuum. A wire the size of a frog hair is wrapped around one end and soldered. Just one problem. The edge of the solder, where it meets the deposited metal layer is a galvanic site. Meaning, that two chemically different metals are joined along the edge of the soldered area.
This is no big deal until moisture arrives. Might be the morning dewfall in an unheated garage, might be a radio that's cold from overnight, when a warm humid breeze blows through later in the day. Condensation is all the moisture you need to turn that capacitor's boundary-between-metals into a tiny battery. The tiny current flow eats the metal away from the junction area, leaving an open circuit. Oxides don't conduct electricity like metals. Turns that capacitor into an open circuit, and the coil's adjustment no longer behaves like it should.
Sometimes this can be remedied without replacing the tuneable can, sometimes not.
Just the same, driving out the moisture isn't the fix, keeping it out in the first place is the only true remedy.