I have configured my system to use an 48 px mouse cursor. When applying a new look and feel theme, it might change the cursor at runtime but load it with default size. Since the size is never actually changed, on next startup the previous size is restored, but it should apply it correctly already.

Changed from Breeze to Breeze Dark, cursor just changed color but was the same size.
I don't know exactly what would happen if we do this with a cursor theme that doesn't have the desired size but I didn't find any guards in cursor KCM either besides the combobox not being enabled/not having a size but it didn't change the value until user did.