New Chaos Reign Hero mechs not showing up in some cases?

Tried traveling between multiple clusters for a long time (at least 1h) without a ANY new hero mech popping up. Given the number of new hero mechs this is highly unlikely. So there may be an issue with hero mech spawns or at least for certain career imports.
I know that these mechs do spawn in Chaos Reign but there may be some cases when they don't.
Is anybody experiencing the same issue?