Practice with low-speed/low bpm bursts (3 or 5-note) and practice the intentionality of alternating your fingers. You want to be consciously attempting to play them zxz/xzx whenever possible.
As/once that becomes muscle memory, then start practicing with faster bursts/longer bursts or streams, as well as playing full songs at a low SR while trying to do the same kind of intentionality in alternating.
You need to build up your conscious control so that it can turn into instinctive play on it's own. Otherwise you'll be trying to play it the way you're used to and either trip over yourself or fingerlock.
(I also don't really get what NM3/4 means. Is that SR or a reference to tourneys? If it's the latter just say 3 star or 3*)