If the frame is out of line from the box then you should be able to warranty it. Also if the brake mounts have't been faced properly, warranty it.
Either way, push back on PX and get it sorted.
It's a warranty in as much as a direct to consumer brand need to sell a bike that can be set up by the consumer. Normally a dealer could take care of a brake mount, but this isn't the case with PX.
@Rhobbs started
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If the frame is out of line from the box then you should be able to warranty it. Also if the brake mounts have't been faced properly, warranty it.