i am not sure, if i understood this correctly: you posted in september, that your watch has an issue fully displaying the ° sign on the screen. right?
As you did not tell, what already was tested, my first thoughts would be to check, if this issue shows any reaction to changeing the watches font size? "Bold" set active? Does changing this have an impact to the issue?
and which complication/app do you use to display the temperature? the default one shows a from-to-scale.. Do you use a third party app for this?
Did you already try to un- and repair the watch?