Windows Explorer: Cannot "Remove the following properties"

Windows 10. Under automatic update.

There are two files in the folder: Side-1.wav and Side-2.wav. These were created from one LP.

The File Explorer shows, that the properties are not equal. The Side-2 file have values set for "Title" (equal to 1) and "Contributing artists" (equal to Side) . The Side-1.wav has blanks set for these properties.

I want to modify the values of the properties of Side-2.wav so that they are equal to blanks as well.

There is very clear information in this forum as how to do this. However; the File Explorer refuses to do so: I select the option "Remove the following properties" but the window that follows does not open up a drop-down selection, where I can tick off e.g. the "Title".

The File Explorer is opened as administrator. From the command-prompt the attrib command shows nothing else than the archive-flag A.

Does anyone have a suggestion of what is going on here?

FYI: In my PC there are very many similar folders, but only in a few do I have this problem of different properties between the two wav-files from the same LP.

Regards,
ChG