And Snowbum mentions the following:
Using a dental tool or other sharp small thin object, get right into and lightly scratch the junction of the metal body to the bakelite insulation. Use a tiny piece of fine sandpaper, and rough-up the metal and especially the bakelite insulation, of that junction of the metal body to the hard plastic insulation section. The idea is to sand the junction, including the metal and the plastic, for maybe 1/8" width minimum, and then clean that area with a strong evaporating solvent. NON-oily acetone is what I use, that means NOT using your wife's fingernail polish remover. Then apply a fine line, all-around, it need not be all that wide, with a thin viscosity 'wicking' Loctite. You can also just use the common RED Loctite, if the switch is first warmed up some. Let sit, terminals up, a full day, preferably in your warm house. Then clean the junction with acetone, and then apply epoxy to the junction, completely around. Either 5 minute or 24 hour epoxy is OK; JB weld is also OK; but I DO prefer a slow-curing epoxy. Let it cure one full day, even if the 5 minute type. THEN install switch....being careful to install the proper washer, and to use a socket if possible, and do NOT overtighten. If you overtighten, you can distort the bond and it may leak. Use of a socket is preferable, but a box end wrench works fine. The tool you select may depend on the particular switch and terminals orientation.
I have a new switch waiting on my bench, but unless I get really bored, I may just put up with the weeping.