Scam? A buyer is locking up all of my stocks without paying

New seller here. Doing OA. I recently added some products to my account last week and almost immediately when the product went live, a few sales came in that depleted all of my stock with a Pending – awaiting payment status. As more and more of my inventory became available for this same product, more and more purchases were made that are all under the same pending state. None of the sales has results in an actual shipment yet.

Looking at the product sellers, there’s only one other FBA seller who is also a FBM seller with over 999 items in stock. There’s roughly 5 other FBM sellers too. I only have 20 items available that I had purchased online to resell. I can’t tell who the buyer is either because there’s no buyer information in seller central but im guessing it’s this other mega FBM seller.

Is this a common tactic from competitors? How would you guys deal with this? I’ve already reported as an abuse to Amazon but at a loss on what I can do next. I do see another asin that is exactly the same product but with more FBA than just two. Should I try and switch asins or wait for Amazon to reply? This has been super stressful as a new seller because they have a good chunk on my inventory locked up. Help!