I found out, that the newer version of an card is not open for evolution, when the character-version from that act do not need the card for the evolution.
For example:
Aez, könig von avalonien needs in the older version
Schwert der 5 Vorfahren. The new Version of the King needs no sword for the evolution, so the sword of the newer version cannot evole and has in the upper right corner not an "1" but an "-".
Also sometimes Feerik updated a card but not the character. Then they often made the new card without evolve. (But it looks like since the management changed they make the new card evolvable, even if there is no new character versions. So just tell the names of the cards, that Feerik can make the new version evolvable, too.)
Anyway:
If bouth character-versions need more cards for evolution, there should always be act-cross-evolution possible. As I told before: If bouth character versions need more cards for evolution and cross-evo is not possible, the it is a bug.
For example:
Terrific needs
sarkastisches lachen in the old and the new version, so cross-evolution is possible. If it were not possible, the it was a bug.