Windows showing MBL as full but significantly less data on the disc

I have a MBL and a MBL Duo
Both units are showing as full using the windows view although when you check the volume of files on them as an example the 2T MBL only has 146Gb files on it
The 2Tb MBL has mainly been used for backups via Windows backup
Any ideas please

Hi @BritPete,

Have you opened a Support Case? If not opened, for more information, please contact the WD Technical Support team for the best assistance and troubleshooting: