I have had this happen with 10.12 and 10.11 on rare occasions. To my knowledge, I'm not doing anything different on the occasions that it does happen. It wasn'

I have had this happen with 10.12 and 10.11 on rare occasions. To my knowledge, I'm not doing anything different on the occasions that it does happen. It wasn't Slack-specific as I've only started using Slack recently.