Apple Watch series 1 restart looping

i have an apple watch series 1, about a year ago it forced me to update to watch os 4, while upgrading, it reboot and goes to a sreen said: clear all content and setting... after i select yes, it running a circle progression bar and after finish the progression it reboot again and start asking me “clear all content and setting” and keep looping these steps forever.

please help me as i bring my watch to service authorized they said i need to replace the mainboard and it is expensive, and they said i rather buy new one than repair this.

i feel like apple has trapped me to get new watch, as my watch was working fine until the update, no hard damage, no water damage whatsover...

anyone can help me? thanks so much!

have a good day everyone.