so you dont use the gasket on the pin anymore - just your tube and the pin? correctI had the same issue about 3 months ago due to frequently dismantling everything. On my unit the permanent sealant (clear silicone) inside, underneath the 510 connector were coming apart in small pieces, suspect its due to a lot of powerful ultra sonic cleaning. I removed all of the silicon sealant in that cavity. Took a piece of Teflon tubing (O.D 4mm), cut to size lengthwise and force fit into that cavity. The Teflon tube I.D was small enough for the center pin to fit snugly. To date no leaking and still dismantle everything frequently for an ultrasonic bath. I am sure a piece of silicone- or HDPE tube will work just as well. All said, I am not sure this is the best way to solve it, and Rob would have a valid reason for using silicone sealant in that cavity, but it worked for me.