Material Flipbook on Beam Emitter Issue

Got a weird issue when I applied a material, that had a flipbook in it, to a particle beam emitter. (I am aware that subuvs don’t work with beam emitters, but I figured I could at least use a flipbook in a material to get a result.)

It appears that the flipbook is playing fine on the texture tiles that are odd numbers, but the even ones are playing strangely. I have a 2x2 texture atlas that just has 1234 on it. The flipbook is supposed to play 1234 and loop. But the odd tiles go 1234 while the even ones go 2143.

Any ideas what this is doing? Is there a setting I am missing.