I will try to shead a little light on the subject of how do you reach ikkyu with such problems?
My kohai's technique is very good, nobody agrues over that point. Basic ukemi is also good
Only tobi ukemi is a problem, and yes the student has suffered injuries due to being unable/willing to taki tobi ukemi. Our club prizes ukemi above all and my kohai is an exception which has gotten out of control.
Is tobi ukemi really required? We have to remember that Ukemi is there to protect Uke. So if there is a substitute ukemi that they could take, to prevent further injury, by all means they chould take it. but if the problem lies out of ego and fear, really only time will tell. without being there to witness for ourselves it is hard for us (the forum) to give really good advice. My personal thoughts on the matter is if it isn't really necessary why make an issue of it? I mean I've had students that didn't want to take ukemi at all.Not because they couldn't, but because they wouldn't. But that is a whole together different beast.