I have been following this thread since we got our car, and I appreciate the effort to determine if a certain build date‘s potential defects contributed to the problem. I have thought a great deal about the issue, and as a long time Lotus owner (50 years), an A&P, IA who’s background is in metal and composite and paint restoration, I have a few thoughts. Keep in mind that this is just my opinion at this point and may not prove to be accurate.
Lotus cars have always had problems with their fiberglass/composite bodywork. The early cars fiberglass components were susceptible to gel coat stress cracks , which propagated dramatically after the warranty ended. Our M100 Elan‘s hood skin separated from the underlying support panel when the adhesive failed. Our Elise’ front end suffered ( like most others) from still active solvents in bonding adhesive that distorted the front clam’s bodywork and paint between the headlights and blinkers over time. Lotus now has outsourced the body panel production of the Emira, and the problems still continue.
It is my current theory that the all the bodywork produced for all of the cars so far is defective to some degree.These cars have at most only been around for only a couple of years, so they are still in the early stages of their lives. What separates their condition is the kind of environment they are in. Daily drivers never garaged in rainy environments are much more likely to succumb to the bubble disease than ones garaged, and rarely washed in semi arid conditions. The doors are the most likely to first exhibit the problem as there is a long open void along the top edge that allows water ingress next to the window. It’s obvious that moisture is being captured by some structure or feature inside the doors as the bubbles form in a straight horizontal line. This moisture can come from rain, washing or condensation and is apparently trapped against the outer panel. The apparent porosity in the body panel, no matter how small, allows perhaps capillary effect or more likely vapor pressure to force itself through and against the paintwork on the outside of the panel forming the bubble. As these cars age and are exposed to more environmental events it seems likely to me that the bubbling effect will become much more common fleet wide, perhaps effecting the majority of the cars. It will interesting to see what the percentages are at the 5 year and 10 year anniversaries. Again, this just a theory, but I would bet there are more cars than indicated in the survey existing with this problem that owners are unaware of ( or do not interact on this forum).