@mc_ott, I thought about that, but it leaked the first time from the OEM factory produced toolhead. Maybe that was defective or improperly assembled. After I cleaned it all up (and after many good prints later) it failed again, I too thought I had plenty of torque applied when I replaced it. Maybe it's just a bad head? Maybe it loosens over time? I'm not certain what is really happening. Support is sending out a new head, and I live not very far from there so will look it over thoroughly and keep a close eye on it in the future.
It does have me wondering about any difference in thermal expansion effect between the aluminum and the brass nozzle, and maybe it works itself loose just enough to ooze over time. Certainly there was enough gap between the nozzle and the heatbreak sleeve for damage to occur to the end of the PTFE sleeve. But it also looks like if it was really torqued down too hard, that could crush that tube end.
Maybe it is just my toolhead, but when I put a bit of force on tightening the nozzle, the hotend flexes inside the holder a little. That was the point at which I stopped applying any more force. The nozzle was nearly flush in the head, (within microns) so it seemed like enough, and I didn't want to overtighten as it felt like the whole hotend assembly could spin inside the toolhead.
I've seen some very sexy aftermarket hotends, but they all are designed for a more open assembly. I don't think the Flux toolhead/hotend combo is that much different other than being enclosed. I'm just waiting for someone braver/more skilled than I am to come up with a retrofit plan.