It's a CZ quality issue - as issued from the factory, their stock bedding (and probably even the stocks themselves) are really not fit for purpose (I understand that Olin will replace broken stocks under warranty if the rifle hasn't otherwise been modified, as they should. Still a hassle for the owner though.). If the bedding and cross bolts aren't done then chances are high that the stock will split.

The Brno 602s never had the cross bolts but they were bedded properly at the factory (no bedding material, just proper fitting of the stock to the metalwork, and I think they were better quality timber too) and, as far as I'm aware, didn't have stock splitting issues attributable to poor quality.