When deleting a class and then recreating the same class, the styles are applied again, although they should be deleted - but the real bug is they are not visible/modifable in the builder panel anymore, so you just can’t do anything about that.
I don’t know if this is a new bug something which was never discovered (which would be wondering).
Can you reload the builder after deleting the class and saving the page? This should delete the old styles available to the browser even after deleting the class from the dropdown. After that, you can recreate the class, and there should be no problem.