no, it is not. i do not have cassian unlocked and still have the problem. their explanation has nothing to do with what some people are experiencing.
There are 2 issues.
One has been caused by a bug in the update, changing the materials required for each Era Level. That looks like something CG will try to fix.
The other is the same as it was with Spider Maul. 4 star unlocks have less of one material than needed for all era units plus the legendary. 5 star unlocks have plenty and those who don’t unlock also have plenty.
Anyone who is short of materials outwith these 2 issues hasn’t collected all the coliseum rewards from t1-7.
Capital Games Team