If the user attempts to normal summon a level 7 with Kashtira Birth already on the field, then cancels that prompt the continuous effect of Kashtira Birth disappears, and they can no longer normal summon a level 7 that turn.
Bug reproduction steps
Activate Kashtira Birth to any zone.
Attempt to normal summon a level 7 but do not select a zone.
Right click with the mouse, or click the X icon at the right side of the screen.
You are no longer able to normal summon level 7 monsters this turn.
Screenshot OR error code
Not a replay but a short clip to reproduce it: KashtiraBirthBug
The normal summon of a level 7 should only be consumed after the user selects a zone for their monster.
What OS are you using
Is removing the ability to back out of normal summoning a level 7 the proper fix?
Normal summons and inherit special summons both can be cancelled, but with the latest update the normal summon of level 7 with Kashtira Birth on the field cannot.