Your options:
Use the Mac equivalent of "run as administrator" and any other permissions based troubleshooting. See link below.
Export from Premiere/AME and import DVD/BD compliant files to Encore (i.e. do not use Dynamic Link). This is also a test as to whether it is something more than DL.
Reinstall. Yes, in this context with no more troubleshooting, it is a bit of voodoo. But this is not normal behavior. And yes, I would do more troubleshooting first. You gave a great description of having tried the several easy methods (send from PR, DL from the EN side, etc). I would also create a new Encore project and DL to a short bit of easy footage, then the problem footage. You can also nest a small bit of the sequence you've been DLng to see if length makes a difference.
I don't think there is a newer Mac troubleshooting document.
Troubleshoot system errors and freezes | Adobe software on Mac OS 10.x