I used to do weighted chinups and pullups all the time, with up to 40kg for 6 reps. I was much better at pullups than chins for some reason. A couple of years ago my left bicep twanged during a set of pullups and since then, I can't do pullups without it cropping up. Since then I switched to chinups and my body was suddenly much better at chins than before. Fairly recently I pulled my left bicep from chins, which has now healed but now my tricep cramps up when doing them. It looks as though my body has had enough of lugging me five feet up and down.
I always did chins at a slow pace and maintained tension on my working muscles throughout. I have been doing them on a straight bar, so it sounds like a straight bar does not fit my body type. Has anyone else had to give up chins or had similar injuries? Chins and pullups were my favourite exercises but it's not worth it in the long run.