Guys.... It's called first gear lockout. Many cars, ecoboxes included, that don't let u downshift to first until a certain (and very low) mph. And u should never be shifting into first while rolling anyways
. After 10mph, 2nd gear has all the power u would ever need. Only shift into first at a complete stop.
I'm guessing what's happening, is you're trying to get ahead of yourself and throw it into first before fully stopped. Which combined with a car with a super finicky mt (i.e. 370z) then u will have problems. As stated a bunch of times before in this forum, u cannot rush or "force" this trans to do anything.
#sluggish_synchro_problems