Looking at this it seems the machine isnt getting any better. Press fits are normally ok with certain materials but not pressing steel into aluminium especially when its not actually been machined to fit it in the first place and its supposed to be a permanent fit. The more I read this the more I'm glad I managed to send all my stuff back to them and get a refund although it was a struggle to get it.
I would go with Jazz recommendation and get a grub screw through the side of the alu to hold the nut in place. Remember you just want to dimple the casing of the nut for the grub screw to locate into and get some thread locker on it.