I tracked my last 10 tries of this level and without exception the additional cheese tiles came after the 4th, 8th, 12th and 16th move. So I always end up with 7 cheese tiles and I have never ever seen an 8th cheese tile. As there was no exception, I would say in the current form this level is not solvable. Have I missed something? Is there any way I can force an additional cheese tile to come up?