Yep i had layers 1 to 8 in mix 3 , layers 10 and 11 in mix 4, layers 13,14,15 in mix 5
... up to mix 9. When i migrated it across everything jumped down 1 mix, so i had layer 1 to 8 in mix 2 , layer 10 and 11 in mix 3 . The mixes were correct sizes but the wrong mix number! I just tried to recreate the bug with the same file but it didnt work which is bizarre.
Mick