Some Creality printers appear to ship with firmware that will trigger a heater failure when a serial connection gets established, possibly when enabling temperature autoreporting (which the firmware indicates to support):
Removing the SD card from the printer has fixed this issue for a number of users.
Printer models this seems to affect:
Wow, an SD card has to be inserted for endstops to work My Creality printer ignores its endstops when homing from OctoPrint but removed to avoid a heater failure. Are we to assume Creality is creating an SD card toggling hardware device that will handle this issue and revealed on kickstarter soon?
Different printer models though, I'll probably fall off my chair laughing though once we get the first incidence of both reports for the same printer.
Are Creality paying someone to break things for them? I would happily configure mainline Marlin for them for free, would be almost worth it...