Both, the wheels and seat post, have cracks? Unbelievable!!! Sounds like you had a crash, but don't want to tell us.
Why not sending them back? Afraid Peter find out what happened with the items?
What if it happened with A-brand? And they find out you had a crash? No warranty.
So, what's really the point to send them back? The shipping costs?
Do you know the margins are very small?
Do you know Peter (or other Chinese vendors) have to pay taxes when they getting Items back?
For Peter I can tell you he want them back to see if it's a warranty issue. And how they can improve the quality.
I'm riding on MTB frame of Peter for more than 3 years now. Flawless
I've got wheels from Peter. The rims are flawless. The novatec hub weren't the best (ranchet ring broke), now the wheelset has DT350s hubs. Still enjoying my Chinese product. Especially for the price.