I'm getting back into seriously playing guitar after a few years and I've noticed a synchronization problem. My left hand is much faster than my right hand while alternate picking sixteenth notes, starting at moderate speeds, eg. 120 bpm. To be more precise, when I play a pentatonic scale, two notes per string, the left hand lands on the second note, of each string, faster than the right hand. This ends up sounding as a hammer on followed by a picking of the second note. Curiously the problem is more pronounced when I play pentatonic scales, while it does not seem to appear with, say diatonic modes.
Starting slow and speeding up may not be a solution, as both hands are well synchronized at slower speeds. Is there something I can do to correct this problem?