Well, that was fun.
I had set an alternate time zone on my D2 Mach 1 Pro (Yes, on the current firmware version, no — not a Beta user) on the default watch face. I decided to remove the alternate time zone and then all **** broke loose — it just kept rebooting the watch repeatedly. After it would reboot, I went in to the settings to try to change to a different watch face, but once I got into the settings it rebooted.
It was in sleep mode during all of this and going into the settings to take it out of sleep mode also caused an immediate reboot as soon as you hit the back button to back out of the settings menu after turning off sleep mode.
Tried a soft reset. No change — immediate reboot if you tried to change any settings or do anything at all.
The longer, multi-button press/hold reset didn’t fix it either.
Ended up having to do a “hard reset and delete data“ from the watch. This finally fixed it.
Just reporting this in case the developers see it so it can be fixed in an update (hopefully?). Personally, after all of that nonsense I just had to do, I will NEVER set an alternate time zone again if that’s what happens when you delete it. Basically bricks the watch until you do a hard reset and have to reload everything and lose all your metrics. NO, THANKS. lol