Drupalchat stops after 2 chats

I'm facing a strange issue with Drupalchat. The installation went fine, I'm using "normal Ajax" and when opening the page where drupalchat is installed on, everything appears to work normal. But when I start a chat with another authenticated user, I'm able to send one message then the other person is able to answer it once. But when I try to send the 3rd line, it will not come trough. Basically I'm able to send 3 lines in total, after that, messages will not come trough anymore.

Then when I check /drupalchat/messages,I do see the complete conversation. So also the messages that didn't appear in the chatbox. As far as I can see I do not have any performance issues on my server. Next to that the issue seems to be consistant and appears after every third message that was send.

Anybody an idea?