I was up at the high school last night programming lights for the musical next week and I had an odd "error" showing up. I have a chain of 4 MAC 250's and 4 MAC 300's running off an Express 48/96. The light having the issue was a 300, and it's the last fixture on the DMX chain. At some point during the night, the light started snapping the shutter closed whenever the intensity was brought below 30 on the Express. After it did that, we couldn't get it to open up again unless we cleared the cue we were working with (no, the fixture was not programmed in the cue). We then would go back into the cue, and have control of the intesity again until we brought it down to 30, and then the shutter would snap shut and latch again. We also noticed while it did this, the magenta would be slowly pulsing in and out behind the shutter. The whole time it did this no errors were displayed on the LCD. I did a reset on the fixtures through the Express, and after it reset it came up with a magenta error. I thought maybe it had something to do with the fact that they loaded a cue while it was resetting, so I had the kids reset again and leave everything until the fixtures were finished. No errors came up, but again when you brought the intensity below 30 the shutter latched shut. We also noticed that if you bring magenta up full, the frame goes to white, and if you drop magenta below 13, the shutter latches shut like i describe before with the intensity. Now other than after that one reset, I haven't gotten any errors showing on the MAC itself. We've had tons of errors with these over the past couple shows that we've used them in, so I was beginning to wonder if it is the Express. It's a rental, so I'm not sure of it's history. I was going to try swapping out boards and sticking our Express 24/48 in just to test, but then when we were done for the night and ready to try it out, the light behaved normally and we couldn't recreate the issue. Anybody have any thoughts? Our rental guy is going to have our heads soon because every show we come back to him with 2-3 MACs having some sort of errors. Could it be a termination issue? I have the terminator, but the light is up in an inconvienient spot so I was waiting to see if any problems popped up before I get myself all the way back up there to put it in (they put the light up while I wasn't there, and I had the terminator, which is why it wasn't there in the first place). The DMX between the booth and the stage is brand new, it was replaced last Spring. The only light having an issue is that last MAC on the chain. Any insight would be greatly appreciated!!