I'm honestly not sure if this will help you if you're in this state or not but if your watch reboots and sticks on loading maps, hard power it off (power menu for 30 seconds) then power it back up while holding the Lap button. For my acting up watch this pops up a menu "Restore Defaults" that I'd never seen before. Saying Yes allowed the watch to boot although it had a "Unable to unlock maps" error afterwards but at least it boots right so in theory you can try to side load an older firmware to do an actual system wipe.
For mine it ended up crashing again after a little time and then got stuck in a triangle to fenix splash boot loop and I'm having to get a replacement out of warranty ($199).
But it 'might' help someone recover a watch to working order so I thought I'd post it.