I try to use 200 navMeshAgent to navigation, but stucked.

my project need to use a lot people walk in the road, i try to use navigation to random point.
but i have problems.
first , if i already spawn 150 people above , then spawne another people, i give them a navigation go anywhere , but them stand by spawn point , after few second even more will move or just stucked.

second, if i already spawn 150 people above , use navigation go anywhere, if they hit obstacle, they will stucked.

but if i just has 0~100 people none of the above problem.

and forgive me, my poor english.