Unnatural arm fatigue when doing certain movements

[CaptainProtein]

When I do exercises that require my arms to be close to my torso such as bicep curls, tricep push downs,rows etc. I experience a strange instantaneous fatigue sensation in my right arm causing it to fail way premature even compated to the left side despite being recently recovered from labrum repair on the left arm. This does not occur during exercises that involve moving my arm away from the torso such as facepulls, prone I-V-T scapula exercises,etc. The sensation is pretty ****ty but I would not call it numb, just like all of the strength in the arm vanishes starting at the shoulder and ending in my forearm. I know I don't have a pinched nerve in my spine because I had an mri that was clean. The arm feels normal when not used in exercise. Any thoughts?