I changed the motherboard to a BTT GTR board for other reasons than above and still had the same issues…go figure 🙂 I disabled thermal runaway protection and M600 ran as expected. I used a stopwatch to measure the time it took the HE to get to temp and it was 80 sec. I increased both #define WATCH_TEMP_PERIOD and #define THERMAL_PROTECTION_PERIOD 20 to 80 then re-enabled thermal runaway protection and that seemed to fix the issue. Is it ok/safe to increase these times to that level?
Elevator Multi Material 3D Printer