ipad split view tool bar button to trigger master view causing nsexception

I have a separate storyboard for my iPad, with both storyboards sharing the same code. I added a toolbar to the detail view with toolbar item linked by segue (popover) to the master view. In simulator the app launches, I click the button, the popover appears and the selected row slides onto detail view. However, when I select the button again the app crashes, citing an uncaught exception nsinvalidargument exception [_nscf dictionary localizedcaseinsnsitivecompare:] unrecognised selector sent to instance 0x7f9188d3060. This doesn't happen if I don't include the button and just slide the master on and off. Any thoughts? As it's sharing code with the iPhone storyboard, there are no iPad specific properties, outlets or methods included - I'm not sure if this is where my fault lies.

I was thinking of making the master view remain visible full time but again as they share code did not know how to implement this - it does not bring them up when I start typing.

I'm using xcode 6 and OBJ c. Your know how is appreciated. At work so no code - my apologies. Thanks for your time