Appointments+ sending multiple confirmation emails

Appointments+ is sending multiple confirmation emails to the service provider.

I have not been able to confirm if it is also sending to the client, but the service provider got 5 reminder emails of her upcoming appointment.

It just started happening. The plugin is up to date. The only thing that has recently changed on the website is that Revolution Slider plugin was updated, but I do not see how this affects Appointments+.

Any suggestions would be greatly appreciated. Thanks.