Hello @daniel
Thank you for sharing your experiments!
If I understand correctly you have a BraX3 phone of the new batch, and you flashed the LunarOS firmware and the phone could no longer boot right after because you flashed the (old) preloader (which is only compatible with BraX3 phones of the old batch) when you flashed LunarOS.
You seem to have a backup of the stock preloader (compatible with BraX3 phones of the new batch). Could you share it with the community? Did you use mtkclient to restore it? Cf the following thread:
Thank you in advance for your answer!