Without derailing the thread can you elaborate? From my observations downtime is normally related to weather or slow loading.
Friends I have within the UK/European theme park sector say Mack have great post purchase support, basically if there is a problem they will ensure it gets fixed even if the ride is decades old. Universal clearly has confidence in them as they have 3 coasters from them in Epic.
Intamin meanwhile just aren't interested once you've made the purchase and when they are getting spare parts for the ride can often seem impossible, some parts have a "99 year" lead-time as they literally don't know if or when you will get what you need.
Disney and Intamin don't have a great relationship either... just look how Vekoma have done all maintenance for Incredicoaster or Indiana Jones (at DLP). They seem to only ever go Intamin when no other manufacturer has a ride type they need and then they take care of all the maintenance and issues in house or with Vekoma support. Unless this Space Mountain is something very unique it makes so little sense to be Intamin and not Vekoma.
Mack has a unique issue with their wheel bogie design, where they need daily adjustments to prevent vibrations, even if the track is bent perfectly and no issues are present. Slinky Dog Dash has the same issue and it was present from day one. The other issue with Slinky Dog Dash: riders per hour. Its barely above half of what Big Thunder Mountain can do capacity wise.
I did hear that Compagnie des Alpes, owner of Parc Asterix, Futuroscope and the Walibi parks, are not buying anything from Mack currently. Pulsar at Walibi Belgium (Mack Power Splash) was one of the last ride they purchased in 2016. It is a very challenging ride to maintain and the park had to spend more time and money than they were expecting on the boats. Its also a very, very expensive ride to run: in addition to the LSM launch system, the ride was built in a natural pond with retaining walls, 4 pumps in the corner of those walls and 4 flood gates in the splash area. When the ride is cycling, the 4 flood gates are closed and the water pumps run at a slower rate, keeping the water level at a constant level, right under the running rails. In the brief moment, where the boat is high up on the back spike, the floodgates open and the water rise just above the running rails, allowing the boat to splash around. After that, the floodgates close, the pumps empty the excess water and repeat that every 2-3 minutes. This video focuses on the splash pool:
Seems like what you heard about Intamin long lead times for spare parts is a COVID thing, as it was an issue industry wide. Now, Universal, Compagnie des Alpes, United Parks are all very happy about their Intamin rides. Its not the same Intamin as 15 years ago. Intamin today has a great design team, great support network and great fabrication.
Vekoma is also not the same company they were 25 years ago. Six Flags had every issues in the world with their Giant Inverted Boomerang and Flying Coaster, yet here we are, Vekoma is doing amazing things for Disney and other parks. Vekoma today has a great design team, great support network and great fabrication.