Limit Submissions count is not working

Hello,
when I check the Limit submmissions checkbox in the Settings -> Restrictions of a form, the form cannot be submitted on the frontend anymore, displaying red error message thet submissions has been unsuccesful on submission.

Also I noticed, that, when I go to the Settings -> Restrictions tab, an I hit Save on the form, the Limit the number of times the same value on a field can be submitted checkbox will turn on by itself, even it has not been checked before save.