Sounds like a thermal runaway where a temperature changed too quickly and the code interpreted that as a fire or risk of fire and shut down. A lot of times that can be helped with a silicone sock and a PID tuning. Another thing is the ceramic heater core is going bad and it can’t keep a stable temp above a point. Heater cores are cheap and easy to change. The heater core is considered a consumable part and usually comes in multiple packs.
Old Ender 3s and the like work just fine with PETG. Not sure where you got the impression they don’t.
There’s nothing special about printing PETG that requires a big change over PLA. Printers have been hitting those temps since the rep rap days.
Personal experiences with a cheap sovol that turned itself off when the temperatures went up during a long print.
Sounds like a thermal runaway where a temperature changed too quickly and the code interpreted that as a fire or risk of fire and shut down. A lot of times that can be helped with a silicone sock and a PID tuning. Another thing is the ceramic heater core is going bad and it can’t keep a stable temp above a point. Heater cores are cheap and easy to change. The heater core is considered a consumable part and usually comes in multiple packs.