we had faced this problem in our site, and to solve it temporarily and for short time:
1- we changed the slug generation method in admin panel to none.
2- then we created a temp category, and select all old topics with Persian slug, move them to that category, and bring them back!
this way the slug of all the topics became some simple topic-numbers without any Persian character. there’s a simpler way of using code lines in the link below, that I didn’t try: