I'm pretty sure it is in fact the shift in the center of mass. Specifically it happens docking a wheeled vehicle to a legged vehicle (both quite light). No matter which is being controlled, the legs explode, and this was never a problem in earlier versions. I've even tested to make sure it isn't just suddenly fragile legs by dropping the legged vehicle from a height and it survives just fine. My guess is the sudden center of mass shift (from combined vehicle to just one of them or vice versa) registers as a high velocity impact on the surface, since KSP calculates everything relative to the active vehicle. Whatever they did to mitigate this 1.4.1 and earlier doesn't work anymore. Maybe it has to do with the "fix" for legs being clipped into the surface? Or maybe it's a new bug having to do with the fix for legs always exploding in 1.4.2? In any case it makes bases with legs unusable now.
