When you trap it and start feeding it if it stops eating and glitches out then you need to fly out of render distance and come back and then it will start eating. Also a good way to tame one is to tame a breeding pair of rexes and cryo a baby Rex and when you find a carchar throw the baby Rex out the unclaimed the baby’s Rex the kill the Baby Rex then feed it to the carchar and his taming will go all the way up then hop on it and kill everything around you to tame it.