Speaking as a customer and third party developer/manufacturer that has no ties to Multimorphic (outside of the approval process), my experience has been perhaps the opposite.
I would not tie up a tremendous amount of my family's money or my time in a platform that I didn't believe in or that I felt was unmaintainable - that includes forming a manufacturing company and starting production on a game (and all that that entails) without preorder cash.
As someone that ran an in home repair service for a decade servicing some of what are considered the most challenging games to repair quickly and the most complex (bingos), along with every other era and manufacturer of pinball (I have not yet worked on a Stoner or some of the other pure mechanical manufacturers - there were so many!), I don't find the P3 to be difficult to keep running. In fact, it is a lot more simple to work on than any other pinball game I've touched. Most stuff can be pulled from the game with a connector or two and a couple of screws (if that) and worked on away from the machine. Pretty handy.
I understand and empathize with the frustration, and I am sorry you're having issues.
Glass exploding is unfortunately something that can happen to any game with tempered glass and is not a Multimorphic-specific issue. The way tempered glass works - hitting it on the edge or heating up the edge separately from the center in a cold room (say, with your hands) can cause it to explode. It's an interesting problem that didn't occur with plate glass in much older games. But plate glass is far more dangerous when it breaks, so tempered glass is a necessary evil. Cleaning glass is, thankfully, an area where the P3 can help. The modular nature means you can (hopefully) much more easily clean out the broken glass.
If ordering a replacement sheet from a local shop, you'll want to specify 'no bugs' and 'no logos' or there will be a logo embedded somewhere on the sheet and it will become the bane of your existence as it's all you'll see.
My P3 is currently in a small location (my factory space). It is being hammered on with my personal production copy of Drained, and I also use it for testing updates to my other games that utilize other playfield modules. Usually I run the same game in the factory space for people to bash on (outside of QA which I do on weekends - no one plays customer games except for me, play testing - these are my personal games that I put it for others to play) for a few weeks at a time. It's rare that I do much of anything to any module (aside from cleaning).
There are four pinball games there and the P3 receives the most number of plays by far. Couple that with development plays, and the amount of use my P3 receives is far greater than the average homeowner. Heck, developing a game puts a ton of games on a playfield. I've owned my P3 since 2019, bought it piecemeal when that was still an option, and put far less into maintaining it than I do other (older) games that I own.
I'm not super far from you. So I don't think it's a distance thing.
All that to say, again, I wish you weren't having a tough experience, and I hope you turn a corner shortly and start to just be able to play. Of course that would be the expectation, and there's no reason that couldn't be the case.