"Gritty" Bona Traffic

I was using some left-over Bona Traffic (almost 3 yrs since manufacture) on cherry stair treads and ended up with a gritty finish. It's not bubbles, it's particles. Is this what happens with Bona Traffic when it's old, or should I be looking for another cause?
I strained both the components when pouring into the mixing bottle, and strained the mix again as I was using it, but to no avail. I'm also sure the grit was not on the treads before laying the finish.
If it's the product, could using a new bottle of catalyst be the answer, or do both parts need replacing?
Thanks,
Wally