Glad to hear I’m not the only one suffering this problem. I did give my project to G to look at, haven’t heard back from it yet.
I too transitioned to 4.17 from 4.15, and probably a few versions before that.
I’ve always been able to delete my duplicate actors, but I am unable to discover how they’re replicating. I suspected it was some human action in the editor as well, or some other rare event like loading the level in the editor but I can never consistently reproduce to test it.