Possible problem.
In the last version of the menu, no high level car (eg armoured Kuruma) was saving. It might stay in the garage for the session or a mission, but if I load a new session, I get some random shitty car with the my new reg and the same paint job, mockery. I seem to be credited with the price of the car. This character is just low level, so maybe R* have a control to stop low levels rolling around in top class metal, an anti-cheat control of sorts. It might well relate to level locked cars like the Kuruma. A Halloween Albany stayed, but that's not level locked. I'm fairly sure I insured the cars, but there's a small chance I didn't.
I'll check tomorrow.
Thanks for working on this neat menu.