Paint Damage on Luggage Area Lid

[l_turn9]

Several years ago I repainted my '74 911. After a lengthy research time frame I jumped in and started the prep. The only real damage was the luggage cover had what looked like cracks in the paint which was a repaint/color change by a PO. I sanded the area down to a smooth sub-surface then built it up with Evercoat before sealing it and priming before getting to the top coat. All was well for 1or 2 years when the cracks came back. My 1st thought when seeing the paint damage was that someone had 'over-filled' the luggage compartment, then closed the lid causing damage. But there was no evidence of this when looking at the underside of the lid. The underside of the lid is pristine.
What could have caused the original paint cracks of the PO repaint and then in my repaint?
I am prepping to reshoot the luggage lid and wonder if I should strip the whole lid to base metal or is it possible to fix the problem area?
I will be reshooting the luggage lid in the same Guard Red using PPG color/clear coat. Is it possible to match the previous paint or should I plan on shooting the whole car?

TIA,
LarryT
74 911
66 MGB

[Dpmulvan]

I would take it down to bare metal and see what's going on under there.

[l_turn9]

Thanks. I was hoping to avoid disturbing the factory primer but I guess there's no way around it.. I have spent a ton of hours sanding the whole car and so far I never broke the 1st layer the factory put down. But I suspect you are right - if whatever that's under the paint causing the problem is not repaired I'll just be wasting more time. Now I just need to decide how far I need to sand the rest of the car.
Thanks again -
LarryT