Wow, few things to cover here :lol:
Firstly, it seems very apparent that the parks operate individually. While they may use the Merlin umbrella (and Tussauds previously) to help negotiate a better deal with a manufacturer, I think that it's rare it's pushed from above. The management at Thorpe and Alton know their staff and working procedures much better than the management at Merlin. If Thorpe say "we can handle another Intamin ride because we've hired an Intamin ride specialist this year", then they'll get an Intamin (or rather, they'll put forward a proposal to Merlin for an Intamin).
I think that Rita and Stealth are a little different from the old regime, but now it certainly seems the parks can run autonomously. So teething/continued issues with 13 won't affect Thorpe's relationship with Intamin.
Secondly, as a technician, things go wrong with new stuff. Things go wrong with old stuff too. Things just go wrong. The difference between my systems and Thorpe's though is that if I have a hardware failure, or something needs a reboot, then we just lose a bit of working time. At Thorpe, you're putting people's lives at risk.
So the need for "downtime" is much greater on a coaster, and the need for trained personal to do even the simple things is an absolute requirement. So you will still get downtime even with "reliable" B&Ms. If a sensor keeps tripping and needs an engineer to reboot it, then you have to wait for that engineer to come out.
Now, that doesn't mean the manufacturer is completely free of responsibility, but it's very complicated (as Gerstlauer and Thorpe discovered). Again, the manufacturer isn't 100% free of culpability, but... They will present the entire ride package to the park, yet it's not all their own work. The sensors will come from one manufacturer, the control panel another, the PLUs another, the chains and cables another, the hydraulics another, etc, etc, etc. The manufacturer brings all these things together as a single ride.
If they've chosen the wrong manufacturer for their sensors though and they keep failing (for instance), then it's still the ride manufacturer who needs to find the solution, but often until you are running under the full strain of operations, you just don't know if parts have the performance capabilities promised when you bought them. That's for the individual parts, not the entire coaster (though obviously it does mean that for the park and manufacturer.
I think the reason B&M get such a good rep, is simply because they choose to do things very simply, with very old, tried and tested systems. They also (probably) use higher quality parts as part of their "high reliability, high price" service. As soon as you get complex systems in a B&M, you get reliability issues (I'm looking at Air here).
So downtime is an expected part of safe operations. It's going to happen more often with newer coasters (as the parts are put through their paces) and more complicated coasters.
It doesn't mean that Thorpe isn't responsible. How many "qualified" staff you have available and how quickly they respond (and how well they can do their job) is entirely down to Thorpe. So while they may have not been able to fix Saw's issue in the first season due to parts Gerstlauer outsourced failing (or that were badly designed/configured), they should have been doing something about the half dozen engineers hanging around drinking coffee and nattering while the rest of the park was down.
Again, as a technician, you have bad days where you don't get a break. Sometimes those days are concurrent and you can have weeks without a break. You do the work and you get it fixed, it's your job. It's up to the parks to negotiate that working ethic (wrong word, but I'm not sure what the right one is) in their staff.
Oh, a B&M Hyper, "Europe's Tallest", would be fantastic.