Honestly, I'm a bit surprised your setup works at all. I was under the impression that Core 0.15 exposed some packet deserialization issues that required an upgrade to Armory 0.96.3.
In any event, it would take me a long time to test this on a VM (I use
-txindex and would have to wipe out some Core DBs if I went back pre-0.17). I'd prefer not to do that.

Is there any reason why you're sticking to this particular setup?
Anyhow, I've now gone ahead and finally built 0.96.4 (on Sierra) and it runs fine with Bitcoin Core 0.17.0.1 on Mojave.
Thanks for the input.