env.add_agents can not add all agents

[ElizabethDuo]

Hi MAgent team, thank you for your great project!

I am trying adding more agents by
env.add_agents(handles[0], method="custom", pos=pos_a)
env.add_agents(handles[1], method="custom", pos=pos_b)
env.add_agents(handles[2], method="custom", pos=pos_c)
env.add_agents(handles[3], method="custom", pos=pos_d)
pos_a, pos_b, pos_c, pos_d are lists of xy cordinations without repeat. And all positions are within the map.
Each position list has 64 positions, that is adding 64 agents.
But when adding the pos_d, there are only 24 agents being added.

Any idea of why it happens?
Thanks for the help!