Blocked from champ select chat

It's infrequent (<10% of the time), but happens that I will type a message (usually "adc" in blind-pick, and rather quickly in order to say it first) and get blocked from chat in champ select for several seconds. I can see everyone else posting just fine, but my chat input line turns red and get "blocked" from chat instead of able to chat. I have not been notified of toxic behavior (though maybe once or twice I might have earned it...glad not everyone reports!) or any chat restrictions ever, only a warning about the seriousness of afking back when the family decided to have an impromptu pre-thanksgiving meetup.