Adding a panner and a flipbook node

Getting some unexpected behavior when adding together a panner node and a flipbook node.
Flipbook animation should look like this:


And it works fine normally, but when the outputted UVs are added with a panner UV, odd results occur:

As you can see, the flip book animation becomes jittery and inconsistent. The particularly strange part being that only some of the tiles actually turn out perfectly fine.

Is there a way to fix this?