Can't check in the file with unique file name - "T

We have problem with ePDM(ver. 17.5 (B89)). We are using SW 2017 SP5. It seems that one worker can not check in one assembly file. ePDM gives error:" The filename, which needs to be unique in the file vault, has been used before".

1.Database search returns empty.

2. Firstly I checked that deleted files would not hold a place for this name. Deleted items tab in the property tab of the whole database does't have a file with such name to destory.

3. Then I found this forum thread that suggested to give a permission to the user to delete files. (). When I checked permissions then I found that user doesn't have this permission personally but the group she is in has this permission.

It seems that I can't solve this problem. How should I proceed?

Best Regards!

Mart