Mine isn't a single breakdown but several rolled together from a trip a few years back. It started at Who Wants to Be A Millionaire. We are all in line and are stopped three groups short from entering the show. No big deal, we will be at the front for the next show. So, we wait for what seems like an excessively long time and finally we see people leaving and think it is our turn. Then we wait another 20+ minutes before, finally, a CM arrives to inform us there are "Technical Difficulties" with the set and it will be about 2 hours. So, we opt to leave and head to the GMR. We are in line there for about 45 minutes and are in finally inside when a voice comes over the loudspeaker informing us the ride is having problems and will be shutdown temporarily. We wait an additional 30 minutes with no line movement before finally opting out again. Later in the day, after an afternoon rest, we head to Epcot where we wait for in line almost an hour and a half for Test Track. Wouldn't you know, problems again. This time we get out of line immediately and call it a bad day. We get back to the resort and start joking about the problem with the rides being the jacket my sister is carrying, even thought it is 90+ degrees outside.
So, the next day we head to the MK, planning on staying for EMH evening. We ride a few rides when sister breaks out her jacket. We head to IASM and wouldn't you know, the ride breaks down. At least this time we were already partway through the ride so we got to hear that wonderful song for the next 25 minutes. Finally, when we are off the ride we banish the jacket to the backpack and have an uneventful rest of the afternoon. Then it is time for EMH evening. My DW and parents take the smaller kids back to the resort while my sister and I stay with the couple of older kids. By this time it is cooling off so my sister opts to keep her jacket with her. We head to BTM and wouldn't you know, it is broke down when we get there and the CM is telling everyone it may not run the rest of the evening. So we cross the park, grab a quick bite to eat and head the Space Mountain. After being in line about 30 minutes the ominous voice again tells us they are having difficulties and expect the ride to be down for the next 30 minutes to and hour. Finally, I have had enough. After 6 ride breakdowns in less than two days, I grab the jacket from my sister, jump across the rail to the fast pass side of the ride and throw the jacket in the first garbage can I come to and head back through the fast pass side of the line to get the rest of my party. Amazingly, the ride has been fixed by the time I get back to them in line. For the rest of the trip we had no issues with breakdowns, although I did have to buy a new jacket for my sister. All things being equal, I felt it was worth it.