So my half-lease occasionally tosses her head up when i've got her in cross ties while grooming. I've been riding her almost a year and I don't think I've ever had this problem really. I just started half-leasing her last week so I'm riding her an extra 2 times a week plus a lesson every week. She's just starting to toss her head up and down a lot during grooming and tacking up. What does this mean and what should I do?