A good starting point would be to disable all third-party plugins and see if that resolves the issue.
Make a chat room "read only" for certain users
Is there a way to make a chat room "read only" for certain users, so these users can read the chats but not respond to them?
This is useful for rooms that are used for broadcasting messages.
Unfortunately not at this time -- chats were not really meant to be used that way so there's no changing the behaviour to achieve what you want...
However, in your case, could a stickied header widget not work?
Thank you @julian . I never heard of that. I'll go do some research.