Not bad but here’s what I think may be causing this: it looks like you’re not rotating enough which makes your pull very wide. when it’s that wide you are no longer engaging the big muscles so you are pulling with everything else. the weakest link will fail, in this case your tendons 
Also you might be applying too much power past your hips where again, it’s hard to engage the right muscles - this is just a suspicion.
Take a look at this screen shot:
