I think possibly CZ got a taste of American sales, and then when the dollar tanked relative to the euro, the price stateside for these shot way up due to these exchange rates, reducing sales, so they had to find a way to cut corners, and (perhaps?) outsource the manufacture of some to keep prices down. Didn't help matters the gazillion new turnbolts that have come out in the last 5-10 years to compete with them (Mossberg, S&W, Howa, Stevens, T/C, Marlin, new F. N-chesters, etc.). IINM, their labor cost is pretty high in Czech Republic, so I wouldn't be overly surprised if they have outsourced.
PS. I love my 550s and 452s (fantastic quality for the price), but have not bought any in the last two years, so cannot comment on any recent alleged decline of quality or lack thereof. Oh yeah, I love my CZ pistol too.