Hi everyone, I've contacted Embarcadero support who have advised of the fix. Hopefully this will help anyone in the future who comes across this.
1) shut the IDE down.
2) run regedit.
3) go to
HKEY_CURRENT_USER \ SOFTWARE \ Embarcadero \ BDS \ 21.0 \ Known IDE Packages
4) find the entry
"$ (BDS) \ Bin \ LivePreview270.bpl" and change the data from "Embarcadero FireUI Live Preview Package"
To
"__Embarcadero FireUI Live Preview Package" (so just add two underscores in front of text)
5) start the IDE.