DD used to do that when she rf'd in the Triumph and I HATED IT when she did! She was such a strong child she made the carseat back flex almost 2 inches right into my headrest & shoulder area of my seat. It didn't matter if she was happy or mad, it continued for over 2 weeks before I had enough. If she had been 22 months, I probably could have stopped it, but at 18 months, there was no hope.
It's one of the major reasons I ended up turning her then. Hey, I thought I was doing great to rf THAT long.
Even the doctors were pressing me to turn her around. Basically, it was such a distraction when I was driving, I was worried about all of our safety. It was just as bad as that sudden shrill scream that other kids have occasionally.
Good luck and hopefully she'll outgrow this behavior soon. :thumbsup: