400ex will not go into neutral while running

hi all,
recently i have noticed that i cannot shift into neutral with my engine idling… i can get it into neutral while the engine is off and i can also get it into neutral if i give it some throttle while its running, but if i try to shift to neutral while idling the gearshift lever feels hard to pull and it will not go into neutral. is this normal? or common on these atvs?

thanks