[Dovecot] Question about "Storage keeps breaking" in logs

Hello

I have found this entries in my log

/var/log/maillog.13.xz:Jun 6 17:03:26 buzon dovecot: imap(juanan): Error: mdbox /buzones//18/66/juanan/mailboxes/P7.Bielorrusia/cd-eslpod-enviado/dbox-Mails: Storage keeps breaking /var/log/maillog.108.xz:Mar 4 01:42:09 buzon dovecot: imap(lbandera): Error: mdbox /buzones/0b/11/lbandera/mailboxes/Sent/dbox-Mails: Storage keeps breaking /var/log/maillog.3.xz:Jun 16 11:48:29 buzon dovecot: imap(fjvalderrama): Error: mdbox /buzones/0f/99/fjvalderrama/mailboxes/Asignaturas 08-09/Calculo/dbox-Mails: Storage keeps breaking

I have "rebuilt" those mdboxes with doveadm force-resync && doveadm quota recalc. Should I be worried? Why is this happening?

Regards

Maria Arrea