Seen tons of them. I get season tickets to the local university theater every year, so I don’t know if you’d consider them amateur, but here are a few good gaffes:
During The Kentucky Cycle, a murder scene where one Civil War soldier begged for mercy while another threatened to kill him with a pistol went a little awry when the pistol refused to fire. Poor actor struggled with his prop for quite a long time, but eventually he had to club the guy with it.
At Cabaret with a lesbian friend of mine, we both noticed simultaneously that, in once scene, one dancer’s costume was, shall we say, moved a bit to the side where it should have covered her nethers. Kinda funny; she and I threw each other the ‘did you see that!’ look at the same time.
(on the subject of nudity, their production of Hair attracted some attention this year cuz, in one scene, about 12 fully-nude actors/actresses appear on stage.)
I also remember a lot of struggling with dogs onstage during performances of Annie and Annie Warbucks.
They also performed the ballet Coppelia once; during one scene, a bell fell off a jester’s costume. For the rest of the performance, dancers either adroitly avoided the bell lying on stage or kicked it around attempting to get rid of it.
There are lots of little gaffes, but I’m gonna keep going; they usually do great work. Guys and Dolls, Cabaret, Agnes of God, The Imaginary Invalid, A Flea In Her Ear, Waiting For Godot, Nunsense…all pretty darn good. Later this month I’ll be going to something I’m not familiar with called Picasso At The Lapin Agile, and in the spring they’re doing Cat on a Hot Tin Roof plus a few others.