If something feels sketchy (i.e. numbness) it is sketchy and you should not continue to do it.
Yes, this is an area which needs attention and may require seeing a practitioner to identify exactly what is going on.
Numbness is most often caused by damage, irritation or compression of nerves. Identifying what is causing the numbness is key so it can be corrected.

Is there a coach who can look at your positioning,placement of the band etc. when doing the banded overhead distraction?