If you are stuck in a situation where your Ticwatch E is not booting and you feel that sending the watch over courier is too inconvenient, I have something for you.
Good news: Factory reset can be done if you manage to get into fastboot. (It's very tricky)
Bad news: It requires you to unlock your bootloader thus voiding the warranty. I am not responsible if anything goes wrong.
I have written the full tutorial here. Take a look: https://support.google.com/wearos/thread/12070579?hl=en