Getting 500 error when trying to update page size in admin area

Hi,
We are using the Gitlab EE docker version “gitlab/gitlab-ee:13.4.6-ee.0” on our server. We are unable to update page size getting 500 error Admin Area >>> Preferences >>> Pages. We tried to update some other variables like " Real-time features" getting the same 500 error. Please advise on how to solve this.