Teeth grinding (only on cross ties): always ulcers?

The past few weeks, I’ve noticed one of my mares intermittently grinding her teeth on the cross ties. Is grinding like this always an early sign of ulcers?

ETA – I guess the answer is yes!

Not necessarily…a couple of mine over the years would do that toward the end being on the crossties during a farrier visit. I think it was more frustration and wanting to be back in their stall munching hay with the others. Not ulcers.

Boredom. Anxiety. Of course the anxiety can LEAD to ulcers. But it doesn’t always mean that the horse HAS them. My horse does a bit of teeth grinding as he’s warming up doing his first trot sets of the ride, and then settles in and stops. He’s just anxious to get going.