Problems filtering on a joined element

[Cre]

This has got me stumped.

I can prefilter on other fields but when I try to do it on a field that is a database join it doesn't seem to work.

I'm wondering if it has something to do with the way I have created the full team name via a calc plugin?

return '{fab_teams___season} {fab_teams___grade} {fab_teams___division} {fab_teams___team}';

Any help would be greatly appreciated.