SIM800 closes TCP connection with Hologram TCP socket

Hi everyone, I am currently trying to connect to the Hologram TCP socket, but when I try to do so, 1 second after the AT+CIPSTART command I get an “ok” message and then “CLOSED”.

AT+COPS?
+COPS: 0,0,"Orange F"

OK
AT+CSQ
+CSQ: 31,0
AT+CIPSHUT
SHUT OK
AT+CGATT=1
OK
AT+CIPMUX=1
OK
AT+CSTT="hologram","",""
OK
AT+CIICR
OK
AT+CIFSR
10.191.51.47
AT+CIPSTART="TCP","cloudsocket.hologram.io",9999
ERROR
AT+CIPSTART=1,"TCP","cloudsocket.hologram.io",9999
OK

1, CONNECT OK

(1 second after)
+RECEIVE,1,2:
ok
1, CLOSED

It seems that the “ok” received causes the TCP connection to end, but I don’t understand where it comes from. The same thing happens if CIPMUX=0.
The problem only happens if the sim800 is connected to the hologram cloudsocket, it seems to work fine for google :

AT+CIPSTART=1,"TCP","google.com",80
OK

1, CONNECT OK
AT+CIPSEND=1,4
> test
1, SEND OK

Any ideas ?

Update :
Now instead of “ok” I get “50” before the “CLOSED”.
This problem also doesnt happen in UDP mode, but unfortunately Hologram doesn’t support receiving UDP.