I have a 3 month old 753xt, I suddenly realized yesterday morning that it was out of power( this was strange because it had battery the night before) when I charged it it came up as showing the wrong time :
1) tired connecting it to GPS that didn’t work.
2) then I updated the watch and it’s now running 9.40 nothing changed
3) I’ve also tried a hard reset
nothing seems to to be working and this morning the watch was again dead ( last night it was at 100%) battery