We have an auction plugin that we use and it tends to happen with auction products more frequently, but it happens with regular products too.
It’s worth noting that all of our products have a stock of 1 (each of our products is unique) so that may be part of the reason we experience it more frequently? I’m not sure if other stores are selling products with a quantity >1.
Is there any information I can provide you regarding this that would be helpful?
