I've got a MP duel map and several fx_runner triggered from scripts with use(“fx_runner”). The problem is that these fx_runner work only one time. When the duel map is restarted – which means that all entities are being reset to their default positions without reloading the bsp the fx_runners doesn't show up. I think that “one shot” flag is not being reset for these entities.
For me it looks like a bug in the engine but I'm not an Q3 expert and maybe I'm doing something incorrectly. I've found a walkaround to this problem and replaced fx_runners by func_breakables with “playfx” key and it works fine.

fx_runner's are buggy more than you can even begin to imagine, one_shot won't always guarantee they really do fire once for example!