Smallchat used to be very helpful. However, it seems to be discontinued. There's a serious bug cause you not receiving your customer's new messages without any warning. Your customers may be still waiting for your reply, but you don't know at all since you're not receiving messages, OMG! Please note, this may cause a serious consequence for operators. I re-install their app on Slack and found the issue wasn't caused by Slack APIs. Then I tried to reach the team for reporting the bug but in vain.
Hearty Journal