Its all about timing. All you got to do is time your paradox save game file with you actual save game. When your running the same character on the same account on two separate consoles at the same time your basically causing corruption. Of course to prevent corruption saves are time stamped to prevent loss of data.

So when your buying a car on console 2. As soon as you click purchase on car and its says purchase complete you press PAUSE BUTTON, and RB, RB, RB as fast as possible while holding down on dpad. Press B once you get to INFO menu while still holding down on dpad. Move right stick up to select Franklin and release dpad as soon as orange save circle is done. Accept alert and hover in the clouds until you see a flash. Then dashboard. (All the steps right after buying cars on console all have to be done in about 2 seconds or less.)

As soon as you dashboard c2 have c1 exit LSC and as soon as the car stops turn reconnect internet through netcut. And at the same time while your pressing button on your computer to turn netcut back on press Y on game controller while holding interaction menu. Scroll to style and change outfit and spam B really fast while holding down on dpad and up on the right stick. And as soon as orange save circle dissapears let off dpad and and accept alert to go to story mode.

Also if your donor car had a any sort of cosmetic modification such as a bumper that is a number range beyond that of the car your merging to it will cause issues and your cars wont merge. Usually what i do is change everything to stock that not performance mods then if im merging f1 wheels from an f1 car to a regular car i detune the performance mods to make sure that the mods are compatible with the receiving car. And everything will transfer. The only thing i can never get to transfer is the plate text. But i dont mind that the plate text from the donor doesn't transfer. Because that means that what i had made is a clean merge and not a dirty merge.