I had the same thing with my female ball python. She would convulse at the time she was pooping but did you notice anything else in the cage because she would also vomit up internal parasites. When I took her to the vet all I had to go through was a series of I shot a day for 14 days and with a return visit to the vet she was better. Good luck though I hope everything turns out okay.
P.S. Sorry to hear about your Redtail.