“We hold it was error for the district court to make a blanket exclusion of all ‘other incidents’ evidence by plaintiff to prove a negligence claim involving a design defect. Prior accidents must be ‘substantially similar’ to the one at issue before they will be admitted into evidence. Substantial similarity means that the accidents must have occurred under similar circumstances or share the same cause. The plaintiff has the burden of showing the substantial similarity between prior accidents and his own.” See Croskey v. BMW, 532 F.3d 511, 518 (6th Cir. 2008).