Can you have a look at my thread below, I suspect this is the same issue being discussed here, and I have provided SNMP data:
In short, if additional mount points (drives in the case of windows) are added dynamically and cause the drive/mount indexes to change in SNMP LibreNMS does not handle this properly causing the disk space of one mount point/drive to be attributed to another drive/mount point which was previously at that index.
Some aspects of the data (like drive names) seem to be cached and don’t update when the indexes in the SNMP data shift dynamically.