Hello, I have a brand new Rocksta and one of the things I notice is that the front and rear wheels turn at different speeds. The front wheels spin a good 30-40 percent faster than the rears, depending on throttle position. Is this normal?

No that's not normal. My basher rocsta run equal speed both front and rear nicely sync. Check the rear axle if there's any gear or wheel binding which causes any friction or slow down.

I don't know exactly what the problem was, but I am thinking it had something to do with contact with the brushes. After pulling the entire gearbox apart and combing over every possible mechanical hinderance, the issue was finally solved once I pulled the motors apart and put them back together ...

Glad to hear you've fixed it.