multiple rcon commands crashes server

Hello,

I am playing with rcon commands to make a fireworks from a python script.
Sometimes all the rcon commands come through, some other times the server crashes after a few commands. I could not determine the exact conditions of the crash

Please find attached the server crash report and the script used to send rcon command (found on gitub https://github.com/barneygale/MCRcon.git modified to fit my need)
Execute : ./demo.py <server_ip> <rcon_port> <rcon_password>
level-seed=36150834568
position to enjoy the show : x=206.29, y=99.52, z=25.68

more info :

• The coords are around spawn.

• Executing the script while not logged in the game does not crashes the server, logging in will perform all the fireworks at once. (probably because coords are at spawn ?)

• Adding a delay between each commands helps a little : sometime a 2 seconds delay does not crash the server, sometime it does. (eventually I would like a zero delay for 20-30 commands)
  On the other hand sometimes a 0.1 delay works just fine, I reduce the delay to 0.01 and crash !

• replacing summon commands with "time set 0" does not crash the server.

• Adding "say" in front of "summon" in fireworks.dat (to send a payload equivalent to the case where the server crash), does not crash the server.

• Pasting all the summon commands in the server console does not crash the server.

• Reproduced the crash in a zone not around spawn (2000, 100, 20000)

• I noticed that sending a bunch of commands that do not crash the server has a tendency to help not crash the server when sending the firework afterward. I then can alternate firework, dummy command and the server may stay on a little bit longer.

Looks like rcon does not like summonning fireworks

Please let me know if you need any more informations.

Thanks,
Nicolas.