How I fix Roundcube internal error on 1 email box - no incoming emails

E-mails
1

Hello everyone,
My MX plan and domain are at OVH (Charentenay.com, I opened in 1998 !)
Outside of 1 email box all works well with emails

I have the following problem / I would like to set up :
One email box / end user gets the error message when on RoundCube
"ERREUR DE SERVEUR : UID sort … refer to server log for more information"

End user cannot load any new emails or read the inbox.
Box is not full and not Spam blocked

2

Thank you from the bottom of our hearts for your assistance with this.