Suddenly duplicate folder with capital letters

Hello

Since yesterday without changing anything on my Nextcloud installation, I found all my folders duplicated with capital letters.
I don’t know how it came and what I have to do.
Any idea on what is happening?

Here is a screenshot :
https://cloud.akaii.nc/index.php/s/JJBnBwcAg6BeDXB/download

Thanks in advance for your help.
akaii