@tsarstepan,
No really horrible disasters, but....
I live way out in the middle of open countryside nowhere near a city. The primary town within reasonable driving distance of my area has a branch of the main theater chain that serves nearby cities.
There is also a nearer, smaller, town that has a branch of a different chain of theaters that primarily serves small towns.
I saw Tarzan 3D this summer at the smaller nearer theater. I noticed that the 3D previews were in 2D double vision (as if I wasn't wearing my 3D glasses, even though I was). I figured it was just a glitch with the previews. Then the movie started, still in 2D double vision. I was unsure if my glasses were faulty or if they were projecting it wrong. Someone else in the theater left, I hoped to complain, but I didn't know them and didn't know why they left. I got up and considered complaining, but when I poked my head out of the theater there was a big line. There was also an "employees only" door that was open and clearly led upstairs to the projector room(s). I spent a couple minutes watching the blurry movie from the entrance of the theater room trying to figure out what to do. After a couple minutes the other person came back, and shortly thereafter the 3D was turned on.
I like spoilers and had therefore already read the plot of the movie, so I was able to survive having the beginning of the movie disrupted.
I figured it was a fluke. I've been to that place now and then over a period of decades, and this was my first problem with them.
A week or two later I was at the same theater to see Star Trek 3D. I noticed that the 3D previews were in 2D double vision (as if I wasn't wearing my 3D glasses, even though I was)....
This time I got upset and had an urge to boo and yell in dissatisfaction. I held back. As the movie started in 2D double vision, someone started tapping their foot loudly in a highly irritated manner that echoed through the theater. Someone else got up and left (hopefully to complain). I realized that the loud dissatisfied tapping was coming from MY foot and stopped. The other person came back, and shortly thereafter the 3D was turned on.
At the end of the movie, the 3D stayed on through the big credits with a graphical background, but once the small-print credits started rolling it appeared to me as if someone might have switched the 3D back off (meaning that they would have to remember to turn it back on for the next showing).
I'm thinking now that I'll only use this smaller, nearer theater for 2D movies, and will be heading to the larger town when the next 3D movie is on.