Replace MOSFET AO4433 With FDS6679
They don't look all that similar to me, the proposed replacement has more than 2.5x the gate charge. Look for something with similar gate charge as well as voltage, current, Vgs(th) and Rds(on) ratings. 

Those parts are obsolete but you may still be able to scare some up. Beware of dubious sources though (Ali, eBay etc.)