I upgraded Michael's default car and maxed out the tuning with turbo etc as well as giving it a chrome paint job, custom wheels and alloys etc. I played as this for ages and I am now at about 50% completion and suddenly it has changed to look like the default car but with dollar sign alloys. I have switched back and forth, completed missions etc and it still looks the same way. It's especially annoying for missions where you have to use your default car.
Anyone else had this happen and what caused it? I really don't want to spend money to recustomise everything back to the top spec as it says I have to pay for it again.