P: Grey Point Tool "Could not use the gray point tool because the settings in the file are invalid"

Getting this " Could not use the gray point tool because the settings in the file are invalid" error very often when color correcting scanned negatives with Curves like in this post:

Every photoshop version from ps 6 to 21.1.3 displays the error.
Unable to replicate on ps 5.5 or older.

https://community.adobe.com/t5/photoshop/could-not-use-the-gray-point-tool-because/td-p/10424386?pag...