i have the same experience with Abandoned cart Plugin.
is there a problem in their plugin?
as i know, plugins shouldn't interfere with each other, except on rare situations.
i believe one of these plugins has bad coding...
Here is my discussion with their support:
i said: Your component shouldn't interfere with another component. I'm talking about awocopun which is the most popular component in coworking with virtuemart.
they said: As you know that coupon system is an essential part for an Abandoned cart notification system, and not all our customers use AWOcoupons, it may be a most popular component in coworking with virtuemart, but still not all users use this extension for their store, if we would have implemented an all new Coupon system with our extension it would still be an issue for those who use Vmcoupons, so we have used Vmcoupon with some restrictions so that its helpful for users, if you want we could customize our extension to work with the AWOCoupon but it will be a part of customization.