So you're suggesting that I slather some silicone vacuum grease (and
excuse my ignorance, that's a term I've not heard before) on the parts
and mate them again?

yes, I use vacuum grease for this type of application.

www.mcmaster.com
2966K52
Dow Corning Hi-Vacuum Silica Synthetic Grease 5.3-Ounce Tube
In stock
Quantity Each
1-11 Each $15.55

or equal