USPS issues ? Wtf is speedx? Help

So I've just started using vinted to sell and most of my first purchases came through usps . All of a sudden , I've gotten 8 sales back to back thru speedx and speedx is literally a nightmare. Packages are still sitting at drop off point and it's been a couple days. Is something going on with usps through vinted ? Should still offer speedx? Or is it worth it to only sell with usps? Worried that my sales will slow down if I only use usps