App Designer not finding code

I have quite a large application built with App Designer. The editor seems to have lost it's way in finding code. If I right click on a function and choose 'Go To' then on some function it does not find the start of the code for that function. You have to 'aim off' to the next function and then scroll to the one required. In addition if I add a function using the '+ private Function' the function template code is placed inside an existing function - always the same one - just before the End statement. I either need to cut and paste the 'Function ... End' block outside the enclosing function or just add functions manually.

Neither of these are exactly earth shattering but has anybody else had the same problem? is there a way to reset whatever is keeping track of functions?