Sounds like your bot simply lost connection / the connection was closed (as the error message states) for whatever reason.
Possible reasons I could think of, out of my hat, would be
- Stricter handling not not properly getting replies to PING messages (check your bot does properly handle those).
- Simple connectivity problems (unstable connection) from the internet connection or the machine the bot(s) run on .
- Twitch having issues (which in the last few days it actully did have a bit) which causes connections to drop.
And the messages being “skipped” are the ones the bot tries to send while the connection hasn’t been reestablished, yet.
So the bot sould/should only try to send messages if a connection is properly established.