I noticed this happened on one of my Eagles as well, only one though, none of the others have had it happen, but now I got this level 1400 Argentavis that can't even stand up to a level 303 Had to go find a whole new absurdly leveled one, and that one worked fine, as did the 750. Not sure what is happening, but only realized it must be this when I came across this post, because I swear he had 30k hp when I tamed him, now it's like 5k.