Group chat I have muted still getting alerts.

My work has a group chat that one person tends to blow up at inconvenient times, so I went to the chat name and turned on the slider for “hide alerts”.

It worked until Tuesday. The Hide alerts slider is still on. But now the messages are coming in on both my phone and Apple Watch.

I know the answer is probably just to turn on some kind of focus, but has anyone else experienced this?