Thank you, Yerb! Your tip saved my day!
I’ve also tried Opt-drag workaround of new HD source sequence on-to a new destination HD sequence (acording to Alex Udell workaround in another thread) but clips in a destination multicam sequence are loosing their “Multicam-Enable” setting 🙁
P.S. That’s insane that Adobe ignored the issue with sequence settings change 🙁