@whopping-pochard This is my current wiring for my SSR and PS_ON
SSR terminal 1: connected to switch NO and PSU neutral
SSR terminal 2: connected to switch C and power in neutral
SSR terminal 3+: +5V
SSR terminal 4-: PS_ON

With the Duet 2 I can hold the button for less than 1 second and the board will power up. With the Duet 3 I have to hold the button for 20-30 seconds. My goal is to figure out how to get the Duet 3 setup so I don't have to hold the button down for that long. The only way I figured that would work is if the raspberry pi was already powered on

@Danal
The heater erratic behavior is on the configurator page only at https://configtool.reprapfirmware.org/Mapping
It's perfectly fine on the printer itself! I actually managed to finally get a calibration cube out of it 😄

Thanks for confirming the case of M500.. Yeah 😛 I ended up doing the M307 for H0 and H1 by hand and filling them up there and then doing the M665 and M666 as well. (I'll move them to the config.g since they don't really need to live in the override either.)

So far so good!

I'm all new to RepRapFirmware and coming from old Repetier 8 bit world. 😆