I'm on OSX High Sierra 10.13.1. Tested on REAPER 5.65pre16/64.
Theme zipped via Finder context menu.
It was missing toolbar, scrollbar, tcp_bgsel, some transport buttons, mcp knob_stack, etc.
Theme zipped using Keka, dragging *.ReaperTheme & ui_images folder to Keka apps.
Looks fine, exactly the way it suppose to be when unpacked.
The theme only contain 1130 files.