Most of the time when my Joyetech Cuboids jump out of TC it is due to a high resistance short (coil touching when heated), grub screw not contacting quite right, but most usually it is due to a poor connection between the 510 connector and the post in the RTA.......I have this problem more often on my SMOK RTA G2 due to the non adjustable pin on the base and contact between it and the removeable deck....clean this area good, make sure deck is screwed down tight, loosen a bit and retighten the grub screws (not too tight just a redo), and I check and adjust the coil placement.
Another thing that throws mine out is firing them on a too dry coil.....................make sure the wicking is TOTALLY saturated....I am using SS Claptons at around .28 ohm and I'm noticing that as the coil gets older and more possibly gunked (maybe the wicking is gunked too and not wicking as well) that my temp readings are climbing gradually every day and I go to TCR mode and set a 125 or 130 and the temp seems to ramp slower and stays away from TC cutoff temp setting.......
When I first rewick and recoil if I don't really almost over saturate the coil and wicking well and fill and try to vape in a hurry I get it jumping out of TC, if I let it set a bit before hitting it hard....no problems .........usually.
Most likely time to clean coils and rewick, but in my Boreas the taste of the juice is still great and hitting fine........just the temp seems to climb...so adjust TCR and keep trucking till I'm energized to clean and rewick LOL.
NOTE: If your using a new tank I suggest you check the length of your new 510 connector.....the Joyetech 510 pins are a bit critical, if shoved too far in they try sticking and the tank my not contact well at times
(and from what I hear ruin them).....I've got some 510 screw in heat sinks that contact very well with the pins without shoving them down too hard. I screw these on snug, them mount my tanks on this.......not pretty as most don't set flat on the heat sinks
(some don't even on the stock connector), but this has almost eliminated many of the jumping out of TC issues
(as has the above items mentioned).
In my opinion spring loaded 510 base connectors
(unless they are adjustable) are a bad idea for connectivity, great when everyone use's 510 threaded ends that vary so much in length.............but over all a royal pain especially when TC is used...when the resistance starts jumping around or changing TOO rapidily the Joyetech mods get a brain fart and jump out of TC, I believe that is due to the programming in the chips. It could be eliminated by adjustments in the programming, but then would the TC be as accurate???? So this is my solution, the Kepler heat sinks with adjustable pins.....adjust them to fit your mod, screw them on snug
(not too darn tight please) and I install and remove tanks..............leaving the heat sinks on the mods. So far this has worked fantastic and I have noticed little difference in ohm readings with them attached. Not to mention it will reduce the wear on your mod 510 connector from screwing tanks on and off constantly. The heat sinks are around $5-7 a piece
(cheaper from Slootech)