This chart suggests the DS 106 runs Samba. If so it is probably subject to Samba's shortcomings at file change notification.
See FAQ: Changes to folders are not being detected for info on problems related to Samba.
Whether or not the drive runs Samba, if you see changes in Explorer but not in Opus then the FAQ also has some steps that you can follow in order to get debug information that may tell us what's going wrong.