In reply to Cake:
It's usually excess volume that causes that kind of thing, so I'd suggest it could be a case of too much too soon of both max hangs and repeaters.
Max Hangs, Repeaters and 'lots of eccentrics' sounds like it could be a lot of volume for somebody who's not used a fingerboard much in the past - I know a lot of people still suffering from elbow and shoulder issues as a result of the first lockdown! I'm making an assumption here though so apologies if that's not the case!
How many sessions are you doing per week and what is your rest like between sessions? Are you doing Max Hangs and Repeaters in the same session? I've a client who just increased his max hangs score by 10% in 5 weeks only doing 1 max hang session per week, you really don't need as much volume as you might expect for that kind of training, especially if you've not done a lot of it in the past.
Also worth paying attention to your form. Anecdotally, I find my form suffers slightly in the shoulders and elbows on a max hang (because I'm trying really hard!), and this seems to aggravate recurring elbow issues more than a repeater session at lower intensity. Whilst I don't think the MH causes the elbow issues for me, it can certainly highlights it.
With regards to eccentrics, do you mean pull-ups negatives? If so, I'd be doing them after a fingerboard session - ideally you want to be as fresh as possible for the highest intensity work. Again though, be careful with overdoing the volume of eccentrics as it could be hindering your recovery from fingerboarding. Might be worth experimenting with isometrics at a variety of joint angles instead too, as they may aggravate your elbows less (and could even help improve elbow tendinopathy...).