Issue with column sort - Unknown column

Not quite sure what has happened here - I have two instances of column sorting, for results of Events and Venues.

If I log in and search for Events, I get my results page, I can sort and it all works just as it should.

But if I then try to search for a Venue, I get an error, but only if I have applied the sort to my Events results.

For example, if I sort my Event results by the Date column, and then try to search for a Venue, I get an error about the Date field being unknown.

And the same thing if I sort my Venue results, and then go to search for an Event.

The Events results have a join so that I can search for Events based on a Venue, but I'm not sure if that's causing the issue.

I have attached both search and results pages below.

Hopefully its something simple, as they are working independently of one another - its only when you try one after the other it breaks.

Thanks.