Yeah, the fabric on the Core shorts is fairly poor. From experience of owning and riding with others who own them they are often fairly see through from the start, and certainly end up that way before too long. Strictly turbo only shorts for me now. I think Rapha customer service generally give out a partial voucher if you complain.
It’s strange that they haven’t sorted it because they’ve been the same since launch. The pad is good and everything else solid enough, so they’re only a denser fabric away from a really good value short.