Not able to create a new directory in vault

I use the 1.5.13 version, on Ubuntu 18.04, with FUSE parameter.
In an existing vault (created with version 1.4 and converted to 1.5), I have this error when I try to copy some files in the vault :

It says “Error during the creation of the directory xxx : the file exists”.

I have the same issue using Webdav parameter.

I didn’t have this error with the 1.4 version, it appears with 1.5 version. Then, when I try to lock the vault, I have the same issue than here (Copy files on a vault makes copy/paste fails) : the buttons “Lock” or “Lock and exit” does not do anything, I ckick but nothing happens. The vault seems dead. I don’t know if the two issues are linked or not.

What can I do to resolve this ?
Thank you for your help.