Holy crap! Are these things really that dangerous? According to this article they've had three similar accidents and they still don't know how to fix the problem. 

https://verticalmag.com/news/servo-flap-failure-preceded-fatal-k-max-crash/ 

Yes and no. The blades are incredibly strong but they look like they were made by a 6th grade woodworking class and painted by a blind kid. If you get a chance to check one out up close ask to see the blades. Based on everything else flying it's alarming when you see the flap pocket is just pro sealed on and painted over and there are bolts through the blades. They look straight out of the scrap heap with all the imperfections. The flaps are pretty flimsy looking. Everyone i've ever seen has cracks in the paint and it's very hard to tell what is superficial paint and what goes deeper until it's advanced. Note it and watch it.
keep in mind the blades and some other parts are in a pool. You send your blades in and get a different set that has been "overhauled" who knows what operator had them before you and if they abused them or gently tucked them in each night. Kaman isn't really known for their quality control. Each pair of blades and their flaps are mated for life. You cannot simply replace one blade or one flap. You ding a flap or a blade and that whole side is getting pulled. 

There are several flap failures that I know of that have been survived over the years.  It kind of depends on how much collective you have in when it happens.  At high collective settings when the flap goes away the blade pitches violently down and can strike the other blade.  

However, I'm very curious about the determination of flap failure.  If you read the report closely you will note that no one from the FAA or NTSB actually visited the crash site.  It makes one wonder.....

In your 500 princess, the dolphin doesn't want you anyway.

At all the butthurt 500 drivers 

I knew a high time Kmax driver tbat had a servo flap failure. He claimed he was the only one to ever survive it. If I recall correctly, he said he had it in forward flight and aft cyclic lead to an aggressive left role...so he landed it without any aft cyclic.

I've heard of 4 kmax drivers all say they've survived a flap issue. Out of those 4, there is only 1 that I believe. 

always lying about that

I don't think you could control the machine with one servo flap missing. Between being pretty out of balance, the flap also controls the flat pitch/auto RPM setting, one might be able to lower the collective and find the spot where all the blades be somewhat equal, but changing collective settings causes the aircraft to pitch quite a bit because of the rotors are angled away from the fuselage to the sides and thanks to gyroscopic precession the thing pitches fore/aft.

I know of at least two flap failures where the aircraft was landed successfully. One was a previous incident by the deceased pilot in the above crash. 

the Kmax is in part very pitchy with collective in forward flight because the horizontal is linked to it. The whole assembly moves and it's not subtle.

your own question

Presumedly and I've never seen a Kmax in person, the rotors are geared so they dont hit each other, losing the flaperon would cause the blade to go to some nominal pitch setting.Then how do the separate rotor systems mesh? Just axing

excessive flapping can cause blades from one rotor hit the other rotorhead, there's a note in the RFM to avoid "cross controlling" (out of trim flight) usually it only causes the rotor blade to get gouges on the bottom. So I can see that losing one flap could cause severe  flapping and who knows what kind of pilot input was made during the oh crap moment.