If you have a sewing kit in hands, and drag a damaged piece of clothing (that you are currently wearing) onto the sewing kit, it does not give the option to repair. Also if you have an unopened can of food in hands, and drag a sheathed/belt knife onto the can you don't get the option to open the can.

Leather sewing kit is working ok, I can drag a damaged vest that I'm wearing onto a leather kit in hands and can repair it ok. Also you can repair clothes with the sewing kit if you take the clothing off and place it onto ground, so the issue is minor.

This is on the current experimental version 1.11 on a server with no mods.