When I select some custom metadata columns in the View pane in DT (Pro) 3.6.2 on macOS 11.2.1 they are not retained when I leave the group by clicking on a different group and then return to the original group (in which I had selected the column). This behaviour is regardless of which View is selected and occurs in groups, smart groups and global smart groups (ie everywhere I have tested). Other custom metadata columns are not affected. There is no obvious pattern to which ones are, and which are not affected. Any ideas? Thanks 
What data type are they?
One which isn’t retained is “single-line text” (but a different one of the same type is retained), another is “date”