Leaning to one side while running

run holding the pole the other way to balance things out.

I have something similar, but very slight. I just think about it while I run and try to keep adjusting myself back to where I know I should be which often feels like an overadjustment. Not sure how you noticed it, but if you can see it just look every couple minutes. After a couple weeks of this hopefully correct posture will feel natural.

I've had these problems. The tendinitis may be caused partly by your leaning.

It's important that you sort this out before it can affect your other joints.

Firstly, check for strength, mass differences between your left and right sides.

work both sides with compound movements if so.

Barbell Squats

Overhead press

deadlift

If the causes are purely neurological pathways,

then more running, with caution, with attention to that arm, will sort things out.