2. Binding angle - When I moved my bindings over to the new board, I went from a +15/-3 to a +12/-9 angle to test out a more even stance and to see if opening the back foot would alleviate pressure on my knees.
Opening up your back foot can also cause your rear knee to flex awkwardly. If your most recent angles don't solve the problem, or if you develop knee pain from the "pressure" try opening up the front to +21 and shift the rear back to -3. Like a previous poster said, you might find that the issue resolves itself when you become more accustomed to the R/C.