Why does this happen? On Chrome, Firefox, Edge (yes i had to even start that shit for this) and Vivaladi
Check your internet connection and maybe restart your router.
Your connection to the Twitch chat servers is unstable. That or the chat servers are unstable (which used to happen a lot, not so much any more). The fact that it happens on multiple browsers means it’s not the browser doing it.
I’ve had this happen for years 
No solution so far. Tried all the browsers I can think of, no ad blockers, no nuthin and it still happens at times. Very frustrating.
My connection is also very good, no hiccups and it’s stable (yay Scandi interwebs!).
Using a vpn? Twitch wont let me chat with a vpn
Internet is fine, router is fine
Edit: Imagine getting downvoted because my internet and router isnt the problem here.
Im not using vpn no.