That one is not for insulation, since the bottom of the pole-adjustment screw thread is not hollow. It's simply for providing added "grip" to the screw when using a classic connector.
My guess is that your liquid sealing o-ring may be damaged in some way, or it may be the wrong thickness (it should be ~2.0mm) -- I cannot imagine anything else, really. If it's not the o-ring, then we'll need to take a look at the unit in order to find what's wrong if it.
We should get that leak issue sorted out, but I'd take a look at the atomizer, too

From a strictly technical viewpoint, this amount of leakage is an atomizer issue, since it can block your air intake and produce annoying gurgling noises. It's the *atomizer* that's designed to hold the liquid...
The RO40-to-RO50 code bump does not imply that any updates were made. The number is just a code for the production date. There have been no notable functional changes, only production process improvements.