The chrome impact strips on the side wear out fast. We got Brenda's old Cougar when it was only 7 yrs old, and they were already shot. I think moisture gets in there and they get wavy.
Super long shot, but ask Jason (FordPartsCounter) on here.
97 T-Bird LX 4.6 - 80k miles
94 Supra TT Auto - street/strip car
04 CVPI- Brenda's car - 76k miles
95 T-Bird LX 4.6 - fully optioned, owned 15 years, 220k miles
96 Cougar XR-7 4.6- Brenda's car, owned 11 years, 187k miles
88 T-Bird 3.8 - first T-Bird, owned 5 years, 206k miles