There are actually a number of reasons why the first spawns of Angelfish are usually duds. It ranges from the male being too immature to him not knowing what to do to he was spending too much time defending the female from other fish in the tank and missed his opportunity while the eggs were viable. We tend to blame the males as duds but that's not always the case.
I'd be very careful with having 2 mated pairs in the same tank. Good Angels will defend their mates so you could lose one of them if they squabble. Case in point: I had a breeding trio of Angels. That lasted for 2 spawns. By the third spawn, one of the females was beaten so hard for trying to join in the spawn that she had to be removed and I ultimately lost her.
So to ensure you don't lose a pair, I'd consider either putting a pair in a sperate tank or using a divider in the main tank to keep them safe from each other.