I have a folder named _ISTMP1.DIR which is an uninstall folder (presumable created by the install program)
I have tried 2 times to add data to the description field for that folder only to find a day later that the value has been cleared / blanked out.
I coped the folder to my other hard drive and renamed the folder.
Setting the description there seems to have worked (after 15 minutes)
I should mention that the original drive is an SSD whereas the second is an HDD
I created another folder on the SSD and set the description. That too was cleared after several seconds
It won't be the physical type of drive. (Unless it's a removable drive, or formatted in an unusual way. I'm assuming this is happening on your internal system drive.)
If it happens on a random folder as well, my guess is there's something on your system clearing the NTFS ADS metadata.
Some antivirus (and similar) tools are paranoid about NTFS ADS (since it can be used to hide things).
Synchronization tools might clear it as well, although you wouldn't normally have those looking at an uninstall folder.
You could try running Process Monitor, filtering on paths containing the folder name (not full path) and see if another process modifies the folder a few minutes after the description is set.