asymmetric tread on Gazz

I have a 26x3 Gazz. The blocks on the tread on the left half of the tyre are a couple of mm’s behind the blocks on the right half. It wants to pull to the right especially on tar. If I flip the tyre around it only has a slight tendency to pull to the left. I also tried a 26x3 Duro Leopard on the same Muni with symmetric tread and it was neutral. Anyone else experienced similar?