[r-t] Cambridge with asymmetric bobs

[Ben Willetts]

This may turn out to be one of those really stupid questions, but I haven't 
had much sleep this weekend and I just can't seem to see the problem.

In Cambridge S Minor, the three bells under the treble as it moves from 4ths 
to 5ths are a coursing three.  It would therefore seem to be possible to 
call a bob here, using p.n. 16 instead of 36, which will rotate these three 
bells in exactly the same way as a conventional lead-end bob.

'Wrong' then becomes the call when the tenor is 3rds p.b., and 'Home' is the 
one where it's 5ths p.b.  However, calling WHWx3 with these bobs runs false 
after the fifth bob.  Why is this?  It doesn't seem obvious to me that the 
720 should not be true.

Ben