Flickers could be from a few different things.
Some fixtures that have electrical dimmers can cause the lamp itself to flicker if there is something wrong with it.
Higher end fixtures, like the Design Spot, have mechanical dimmers that close flags in front of the optical path (or shutters as they are also called).
So, possibly either the DS has a loose lamp socket (or related component), or the mechanical shutter is twitching or something.
A closer examination of the fixture could perhaps tell you more about what exactly is flickering. It could either be the lamp itself or something passing in front of the optical path (shutter or effects wheel).
If the lamps are flickering, I'd get them fixed ASAP, because you don't want to the lamps to fail from repeated 'hot strikes'. While any problem is serious, that would probably be the most serious of them all.
While it does kind of seem like an afterthought, is the power for the fixtures secured and adequate? If there is a voltage drop, I'd suspect the lamps to not like it much at all. Just an idea to try and help you out...
Regardless, I'd recommend calling into the office to have a chat with them about the issues, especially since multiple fixtures are displaying the same symptom.