Subfolders disappear when entering site's root folder

[themadturk]

I have various FTPS virtual directories running on IIS on Windows Server 2019. The virtual directories are all present on a NAS (some Dell device, I don't know which). When FileZilla users log on to any of the FTP sites (we are on the latest FileZilla client for Windows), they can see the folder mapped to the top level of the site and all folders beneath it as expected:

default connection.png (29.73 KiB) Viewed 4347 times

but if they click on or arrow up to the "root" folder, the top level mapped folder and everything beneath it disappears and can't be accessed without starting a new FTP session:

root-folder.png (33.12 KiB) Viewed 4347 times

Is this a bug or expected behavior? Is there a way to prevent users from clicking or arrowing up to the root folder and losing access to the folders below that?

[botg]

For some reason the server doesn't include the pre-prod directory when listing the root directory. Contact your server administrator or server hosting provider for further assistance. In case you are the server administrator, contact your server vendor for further assistance.

[themadturk]

Thank you! This gives me a direction to look.