Thanks for your reply.
No, the workaround script did not output anything. And you’re right, the problematic repo is missing from any of the storage paths - I can’t find it in the legacy or hashed storage. It seems this repo disappeared someday - and I don’t know when.
As I posted in other topic Cannot delete project w/o repo our developers sayed this repository (project) not needed anymore, so i tried to delete it.
After all, gitlab-rails destroy project snippet restored this project w/o repository - so i can accessing issues, pipelines and so on - except repository, obviously. Project successfully moved to hashed storage and upgrade proccess continued