Setting the public flag is definitely necessary, objects inside package A can’t refer to subobjects in B unless they’re public.
As you have discovered EDL is still quite experimental in 4.14. We’ve made several big fixes to it in 4.15 but they’re not 100% done yet. By the time the first 4.15 preview hits EDL should be a lot more stable. The version in 4.14 has a really hard time with subobjects-inside-subobjects which it sounds like you were relying on, so it would be a lot of work to get it working on 4.14 vanilla.
If it’s critical that you ship on 4.14 we’re putting together a branch with some of those fixes, so once that is done I can give you access to that info, but it will be a lot of manual maintenance. Or, if you have enough time to wait for 4.15 I would recommend disabling EDL until 4.15 is released, then turn it on there.
I’m not 100% the fixes on 4.15 will resolve your case, so if you want to make a minimal sample project I would be happy to look at it and verify, but I would only do that if it’s time critical on your end.