[Lombra]

What immediately strikes me is that you're using destName in the UnitIsUnit check. I don't think that'll work unless dest is a group member.

You could try doing UnitisAllowed(destGUID)) instead, and then doing something like this instead:

local function UnitisAllowed(guid)
	for key, val in pairs(addon.CONFIG.units) do
		if UnitGUID(val) == guid then return true end
	end
	return false
end