If this problem is primarily affecting Cobra trailers with fiberglass
tops, rather than aluminum, I wonder if the difference in thermal
coefficient of expansion between the two materials might be playing a
roll?

On early Stemme S10-VT motorgliders, the spoiler control rods were
aluminum in an otherwise mostly carbon fiber wing. The spoiler over-
center locks were at the fuselage end. As the temperature dropped with
altitude, the spoilers would first start to come open and then
sometimes even open all the way with no pilot input. Problem was
solved by changing the control rods to carbon fiber.

bumper
zz Minden