dovecot - Nov 2020 - doveadm altmove not working for some folders

dovecot 2.2.33.2 on Ubuntu 18.04

I am using dbox with altmove to save storage space on mail server
I got strange behaviour with one email box where folder content
Archives/2018 is not moving
but other folders
Archives/2017 and Archives/2019
are moved to the alternate storage server

Well I dont know howto start to resolve this

regards