I've done some choral speaking. We've been harvesting zoom performances through isadora and editing live.
I've found that unison works if all of the actors can pick up the cue and agree on a tempo. When they try to follow one another (like they might in person) it creates problems. We did some rehearsal work around setting the tempo of the line. Having actors repeat in sequence until the line sounded the same with each delivery. Then we explored different methods of cuing.
I'd be happy to pop on a zoom with your team and see what we can do.