I'm not taking shots at MME here at all, just stating what I see.
If this is so, i.e., they are the two piece "avoid at all costs valves" then you need to decide if the heads should be pulled and all the valves replaced.
Second, if this is a hydraulic roller lifter camshaft,
, that right there is part of the problem.I suspect what happens is that even though that profile is "represented" as "streetable", it has a timing pattern that is not cushioning the closing of the valves. Most likely that is why the other valves are showing signs of "over reving".
If you search on this forum you will find another thread very, very similar in results to this with MME as the builder with mileage showing much less then yours.
If this is all a result of parts selection by the builder, then I personally would have to consider that as much more then an oversight or a coincidence. Particularly when there are two engines here in the same broken condition.
My personal opinion is that you just can't build these engines with components like AFTERMARKET roller camshafts and expect them to have a longevity significantly longer then an engine built to run in Pro Stock drag racing.
With 4,500 miles on it, the way I see it, that's 9,000 runs down the 1/4 mile...allowing for the return trip.
That thing needs to be serviced maybe after every run and certainly every 10 runs.
It is the nature of the beast that "you" have spec'ed and had built. It is a race engine no matter how you cut it and is going to have a failure, and service rate of one.
That really takes the builder off of the hook here. YOU have to know what YOU are spec'ing here.
The builder can only help make selections based on that criteria.