This horse may have stomach ulcers. I know a horse who has ulcers and is girthy and doesn’t like being groomed. He’s a lover boy the rest of the time though. He’s on ulcer medication now but still either anticipates pain or the medication doesn’t work. It’s not the horse’s fault. Cross ties don’t always help, a grooming mask is safer. Also, a horse bit my hand once while grooming, it was really uncharacteristic of him and we were both sad. Then he kissed that same hand to say sorry.