Update: Turns out the bearings were worn/pitted. It was allowing the axle to shift under force (both braking and stopping). If I had waiting much longer to address it, it might have put enough stress on the axle to the point where it could snap it. Yikes!!

New bearings are on order.

I was open to getting a new hub or new wheels instead, but I have Quick Release design and apparently they don't carry that anymore since everyone has gone Thru-Axle now. My bike is only 2 years old and it's already out of date!! lol