Anyone returning their coins and having issues should direct the Royal Mint to their own website where they confirm:
“What are Proof coins?
Proof coins are the highest quality commemorative coins. Their sharpness, detail and finish are unrivalled, making them perfect for collectors looking for highest levels of craftsmanship and detail.
The dies used to strike Proof coins are hand-finished to ensure that all imperfections are removed. Blanks are fed into the coin press by hand before being struck up to six times, at a lower speed and with less pressure than other finishes, to preserve the finer details of the design.
After striking, each coin is inspected for imperfections. The dies are cleaned with air between each coin to ensure that no marks or imperfections are caused during striking.
As a result of this extra care and attention, no more than 50 Proof coins can be struck within an hour. Proof dies are also regularly reworked to maintain the quality of the finish. Each Proof die may only strike a few hundred coins before it has to be repolished.”
https://www.royalmint.com/discover/coin-collecting/striking-standards/