I have just restored an accidentally deleted mail folder (in Maildir format) that was generated on a linux machine (Ubuntu 24.04.1, Postfix 3.8.6, Dovecot 2.3.21) and backed up to OneDrive from the command line with Duplicacy 3.2.3.
I used Duplicacy Web Edition 1.8.0 to browse for the missing mail folder and restored it to a Windows 11 PC. Everything seemed fine until I uploaded the files back to the linux box and tried to view them, at which stage I noticed that they were all zero length. Tried several times with different revisions, consistent results.
I then restored the files from the linux command line instead, and everything was fine.
I run a daily “check” schedule from the windows machine including the “-chunks” option (having been bitten by write-only backups in the past) and there are no problems shown.
This therefore seems to be a bug in the restore process rather than the backup process, and specific to either Windows or the GUI.