Hi @Cloud_Geek_82 ,
I suggest you go to the same directory of the problem file and check if there is an hidden file with "~$" symbol with the same file name. If you can find this kind of file, please remove it and confirm if other users can open it. Then please make sure the User A have permission with Delete, try to provide the full permission to the User A.
If this issue still existed, I suggest you confirm if this support article is helpful:
If the response is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.