Doesn't surprise me that some fit different from others
There's always going to be production tolerance differences with both the bike and the FMF parts, I bet there are a lot more tolerance issues with FMF than the stock bike
Crashing can bend the subframe slightly, might be hard to see but would certainly change the alignment of the parts
There can be any combination of these variables
There's no such thing as perfect fit for every acc, the problem is that fit and finish of factory bikes is so good that margin of error is much narrower than on older bikes
I've always said "Bolt on = adjust bike or part as necc" and "universal fit = fit's nothing well"