When installing Tact assistant on 2nd device please make sure to follow the below instructions to disable the calendar from the settings. It is recommended not to connect the local calendar on the second device. Even if already connected to local calendar on 2nd device please follow these steps to disconnect the local calendar.
Go to the iPhone/iPad Settings -> Privacy and Security -> Calendars. Under Calendars, locate the “Tact” app and switch off access to the calendar. This will make sure that the 2nd device is not connected to the local calendars.