If you are having a nagging problem with metal halides, I would start with checking the line voltage, do it at the base of a pole with the lights on. I find a lot of 208v 240v mix ups or sometimes to much voltage drop. Also double check the ballast and lamp, there is a 1000w pulse start out there but it is not as common as the ordinary 1000w metal halide (probe start). If you have a solenoid(wiggy) tester with continuity tester you can use it to test a couple of things, first the open circuit voltage(never use digital meters or testers on this as they can be destroyed) go to a fixture working without the problems and place the tester across the socket from eye to shell, and both eye and shell to ground. remember how that looks and go to the trouble ones to see if its the same. You can also test the capacitor that way with the continuity tester, take out the capacitor for testing place the leads of the tester across the terminals it should glow for an short time(seconds) and then get dimmer and dimmer until it goes out. usually caps bulge or leak when bad or going bad, but not always. capacitor plates can go open or be shorted together and even change capacitance, this will cause outages or dim lamps. Also beware of bad product it seems to be happening more these days, I recently had 7 out 12 MH lamps that cycled(on and off) right out of the box. But that one is a long shot.