Were you giving them anything else apart from the Bravoxin?Most are regular aged 1 to 5 crop. most condition scoring 3. Only 2 or 3 nervous ones, so little stress. I have a way to hold head against race with right fore arm (injector in right hand) with left hand parting wool and raising skin. The first one that fitted did IIRC struggle a little. She was down by time I had vaccinated 3 more in race.
Its annoying me, not having seen this before.