Abandon cart emails being sent to customers no matter what

@frangipani - @Mailbox Manny is on the right track.  Typically if you’re getting the wrong people in a Flow, the first place is to check is the Trigger Filter and/or Flow Filter rules.  

One possible explanation that I’ve seen in the past is if you are using a third party app for your Subscription orders, and you’re only getting Abandoned cart emails for those, it’s possible that it isn’t passing the Placed Order event to Klaviyo if it’s handled outside of Bigcommerce.  

Although you did mention that some “Placed Orders” events are showing people as not having placed orders, this is a bit strange.  But on the same hypothesis, some Subscription platforms do also process one-time purchase items as well - and if it doesn’t pass that purchase into Bigcommerce (or that app isn’t integrated with Klaviyo), then Klaviyo doesn’t have the data for a “Placed Order” event. 

Finally, did you implement a custom Abandoned Cart event/metric to Klaviyo?  In your explanation, you mentioned you’ve tried adding things to cart (but did not start the checkout process) yet still received an email from the Abandoned Cart Flow.  Natively, that Flow should only be triggered when a “Started Checkout” event has occurred (user enters in an email on the first step of checkout).  If you’re getting an email before this, then I suspect you might have a custom Abandoned Cart metric/event documented here: Guide to Creating an "Added to Cart" Event for BigCommerce

This highly depends on what Subscription platform or software you’re using, how it’s integrated into Bigcommerce and/or Klaviyo.  So if you can share some context, I think we can help you figure out what’s going on.