Has anyone ever come across this?

I am getting a victa tornado ready and I took the 2x 18in blades off and put ga spares BNC6490 (victa 19s) on but they dont clear the chassis.

As far as I know the tornado takes 19in blades, with 18in blades the cut measures 18in but with 19in blades its 19.5in. The blades measure 120.65mm long as they are meant to.

The blades don't look strange but have I got duds?