[ ! ] Category permalink problems

I have a problem since upgrading to 3.1 (now 3.1.1) with category permalinks. Till now I used one of default permalinks formats “/%year%/%monthnum%/%day%/%postname%/”.

With 2.9 everything worked like a charm for ex. https://url/category/cat_name/ . And it still does if i restore form backup to old version.

With 3.1 when i try to open https://url/category/cat_name/ I get 404. Posts works fine, problem is only with categories. So i guess there is problem with taxonomy or something. I’m out of clues.

For now I use defaul permalink and it works, but afaik it hurts SEO pretty much, so i would like to solve this somehow.