Hi Caro.hi my friend ,
well ... i think the problem is Device Care app ... this new full theme is without it ... try it when you can
v6.3.02
don't uninstall the updating of Device Care app anymore
It's progress, but not ok.
Show what the result.
My Phone restart 1 time in bootloop and after no access to System UI. My phone restart on Safemod systemUi.
Take care my friend.