I'm having some problems with my V6 hotend leaking. After I swapped my nozzle in my Prusa i3 Mk3S, I've been having material seep up the threads of the heat break and leak on top of the heater block. This has happened several times and I usually don't notice until it starts dripping down the sides and making a huge mess. I replaced my original hotend after a particularly bad leak a few months ago, but I'm still having the same problem with the replacement. What I assume is happening is that I'm not able to get a good seal against the heat break when the hotend is in the printer. I've replaced the nozzle with the hotend out of the print head after cleaning it up and I usually get a good seal then, but disassembling the print head every time I want to replace the nozzle is a hassle. I haven't had this problem with other printers so I'm not sure why this is different. Does anyone know why is keeps happening? Has anyone found a good way to make sure you have a good seal before printing?