Unable to Create Non-trailing Slash Redirect

I've recently enabled non-trailing slash to trailing-slash redirect in one of my websites through htaccess. After this, I found that I'm unable to add new posts or make any changes in the existing posts/pages.

This is what happens; While saving the draft for new posts or while updating the existing posts, no new data is getting saved. It either shows the previous data(for existing articles) or shows no data (for the new articles).

I was thinking it's the issue with any of the plugins. I started deactivating plugins to check this. However, it didn't help.

Then I raised a call log to my host. They also couldn't resolve the issue. However, they got a way to resolve it- using Classic Editor instead of Gutenberg Editor.

I wanted to use the Gutenberg editor.

I know this is not related to GP. Still, if anybody got any solution to this strange issue, kindly share it!