When I went there this weekend to see a movie, the GM said she'd let me in if I didn't come out to complain about anything. What?? If something is wrong with the presentation, I can't complain about it? In reference to my last visit, she said something like "We don't know what lateral waves are." Ok, I did not say that. I said lateral guide roller, and anyone working in the booth had better know what a lateral guide roller is!! Then she said "We're not perfect, and we're never going to be." Grrrr!!! Help! Take me to a place with real projectionists who care about Film Done Right.
You find the address of the corporate HQ of that company and tell the Pres. of the company (or whatever) the same strory you just told us!
No self-respecting manager of ANY business should EVER, EVER say something like that to a customer!
If my boss ever got a report like this about ME, he'd be on the phone, reaming my ass, in approximately 0.68 seconds! If I pleaded for my life and promised never to do it again he MIGHT let me keep my job!

If the manager in question is behaving as you say then it's time he/she looked for other work.
It's a tough spot to be in. You try and TRY to teach people how to do things the right way but as soon as you head out the door, they all go right back to the way they were doing things.
All you can do is keep on telling them until you're blue in the face.
As much as it always seems that you are telling people what's wrong you need to make sure you tell people about the things that they are doing RIGHT. There's an old saying; "Criticize quietly and praise loudly." There's a lot of wisdom in that saying as long as you don't let yourself become like a cheerleader.
Another thing you can try to do is explain to them (in as much detail as they can take) WHY you are pointing something out. For instance, in the case of a weaving picture, you can tell them that an unsteady picutre causes customers to get headaches. Say to them that it's the PROJECTIONIST'S responsibility to see to it that the customers don't get seasick watching a movie.
Yes, it's over dramatizing things a bit but it is substantially true. Unless you point things out to them in a way they can understand they aren't going to want to improve things.
Finally, when you DO finally get people to improve make sure you document it to your superiors. Send an e-mail (or whatever) to your boss and "CC:" it to the theatre manager. The idea is to try to get them to understand that you are on THEIR side.
Other than that the only thing you can do is keep on hammering on people until you pound it through their skulls. It's not a nice thing to have to do but sometimes you have to do dirty work like that.
#1 Poor pay rate
#2 Horrible uniform (Cinemark's plastic suspenders and bow ties come specifically to mind)
#3 Abuse from techs or managers (aka: get blamed and yelled at any time the equipment breaks)
Think about it. All of those problems could be eliminated, or at least the second two. No one will keep working a job if they are unhappy. Take care of your staff and your staff will be loyal, take care of you...and STAY! No more re-training staff over and over and no more sloppy presentations.
In my town usually projectionist doesn't pay in other theater. However I usually pay in some theater because I want to show my ticket when I'll exit claiming for something... 
If you are a collegue and you don't know well the projectonist, it could be inappropriate to exit claiming something: one colleague can thanks you for the help, another one can be annoyed.
But if it is the same chain, I would think that your colleague should be happy for the help.
Surely, the manager shouldn't reply to you...
I'd say to that manager "why should'nt complain if there is a problem that can be easily resolved? I'm available to help the staff with the problem, customers has paid to see that movie."
You have to analyze the people before make any comment... 
Bye
Antonio
The upper echelon should only be happy that someone gives a darn! especialy when someone works for the same company! Where's the team spirit??You can't be faulted for taking your employers business at heart, the problem seems to be with management localy.Latteral Rollers???, it's tough explaining to some booth attendees that there are no fast forward ,pause or eject swithches on the projectors.------------------
It is better, I have found, rather than to lecture or take a "holier-than-thou" attitude, to instead, "suggest" an easier or better way to do a given task. They will respond with gratitude.
"You know, that's not bad, but let me show you what I usta do with that" kinda thing.
The end result, is less abandoned performances, less film damage, better performances, and after all, isn't that what we're all trying to achieve here?
Most of our concession people start as freshmen or sophomores in high school, and at least 90% of them work until the week before they have to leave for college. I have a long list of "former" employees who are willing to work during Christmas vacations, etc.
I have a friend who owns a theatre in Hardin, MT (about 80 miles from here) and two of her staffers have been there over 12 years!