If you have a Google account linked to your Calendar on your iPhone,
and you have linked your Google Calendar to TimeBlocks,
your event may appear as duplicates.
However, it's actually the same one,
so deleting one will erase both of the synchronized schedules.
To resolve this, select the TimeBlocks Menu - Connect - iOS Calendar.
Click Advanced Connection Settings and uncheck the Gmail account.
(Names like Gmail or Google Calendar or @gmail.com may be displayed differently depending on your phone.)