Loss of column and adjusting column width

When trying to adjust column width all columns except one collapse and only recover in options>preference>entry_table> - toggling 'fit table horizontally on screen restores it until trying to manage columns.
Also on my version there appears to be no means of setting columns despite it being shown in the help pages

Dear Graham Ellender,
Thank you for stopping by Jabref forum.
I believe the issue you encountered has been listed among JabRef bugs (https://github.com/JabRef/jabref/issues/6690).

The issue seems to appear only when more than 2 files are opened. Could you confirm?
Please, could you mention which OS you are using?
The current work around is to open only two files at a time.