Do you have Everything installed? If so, try telling it to rebuild its index. Also, make sure it's configured as per Integration with Everything [Directory Opus Manual] including indexing attributes, for best results.
If not, or if that doesn't help, please show what's inside the problem folder, as that may be a factor.
Settings under Preferences / Folders / Folder Sizes / Junctions and Links may also be a factor.
The folder contains my music collection of mainly MP3 and Flac files. There are 112'464 files in the folder. (see Sample of folder contents screenshots)
I have the identical folder / file structure saved on a NAS - Opus reports the correct size on the NAS folder. (see Sample of NAS Folder screenshot
)
I have noticed that the folder sizes WITHIN the top level folder are shown correctly - when comparing the Opus folder size to TreeSize. (see Folder Sizes screenshots)
It seems that only the top level folder is showing the incorrect total size.
I have repeated "calculate folder size" within the second level folder - (d:\Music - Main\ ) -
the size recalculation dialogue box appears, and folder sizes recalculated.
I have also repeated the "calculate folder size" within the top level folder - (d:) - and the size updated again - but remained incorrect.
Try turning off Preferences / Folders / Folder Sizes / Use Everything to calculate folder sizes where possible and see if the size calculates correctly, that will at least show if Everything is involved or not.
