If we assume there are zillions and zillions of extraterrestrial intelligences broadcasting radio, chances are at least a few zillion base their unit of time on periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom (https://en.wikipedia.org/wiki/Caesium_standard)

Such civilizations would have a unit of time that’s a rational number of seconds. That would make such clashes possible (but very likely not likely, depending on how likely it is that a civilization uses caesium 133 as the basis for its clocks)