Do this if you're stuck at 95% completion

[Azzooorr]

I followed a guide all the way through to make sure I don't miss any missable missions, followed everything they said and only got 95%. Go to the import garage in Portland, walk around the place to view the cars you have then go over to the crane. This will pop the 100% trophy. 

 

Or watch this video i found that helped me.

 

 

[Berzerkgod313]

I don't believe the issue has anything to do with looking at the vehicles, it has to do with the crane. When you send the last vehicle, if you do not wait and watch the crane fully deliver the vehicle to the boat, then you do not get the percentage that is associated with that. The reason your "fix" works, is because you are going back to look at the crane. Hope this helps.