Bot repeats command replies infinitely

Hi,
Thank you for all your hard work on this plugin. It’s exactly what I’m looking for except…

When I set up commands, the bot replies to the command with my chosen response repeatedly forever. It replies about once every 2 seconds, and if I issue the command again, the rate of replies doubles (for predictable reasons).

Looking at the log, it appears that the bot is re-scanning the full history of my chat with it at a regular interval (several times per minute) and responding to every command each time it does so.

I haven’t seen anyone else reporting this kind of behavior so I’m at a loss for what to try. I have an SSL certificate; I’m using PHP 7.1; the latest version of this plugin, and WordPress 4.7.

Thanks!