Misreading resistance by a significant margin (for TC), popping in and out of TC randomly, showing temps in the 800s when temp was set to 450, showing random strings of numbers (say, for example 346712) on the screen when fired were the major issues I experienced.
Though maybe it was the
kayfun 5 that was the issue so I tested all of them with my raven's moon rta as it has the best possible conductivity and rock solid connections. Wrapped spaced 316L SS
coils, cleaned all the contacts, and the steam engine CSV setting. Experienced the same issues. Couldn't figure it out, contacted the vendors, vendors asked that I send them in for testing, and was told each time that the
device was defective. Of course, don't know if it was the chip, the wiring, the 510, or something else.