Pain in back of shoulders?

[Asclepius]

So for a little while I have gotten pain in the back of my shoulders (think right on the posterior deltoids or right below them) every time I pull something apart (like holding something at navel level and trying to pull it apart).

Recently I've been doing more push presses, and this has been causing the same areas to hurt for some reason (doesn't happen when doing just overhead press, probably due to the position of the arms when starting the movement).

Any idea what this could be? It's starting to get a bit bothersome.

Thanks!

[Brutus]

I also feel some soreness in this zone after an intense sesion of planche leans or tuck planche (static) series on Parallel bars