Hi,
First, please download again the reminder plugin on our website in your order details and install it on your website to make sure you have all the latest patchs.
Normally, the reminder plugin should not send an email for a cart if an order was made by the customer afterwards.
So if reinstalling the plugin doesn't help, we would need that you give a screenshot of the settings of the reminder plugin.
Also, normally, after an order the cart of the customer is cleared.
How do you have configured the "clear cart after an order is" setting of the HikaShop configuration ? Which payment plugin are you using ?