It might not be nanoseconds, but something that's a power of 2 number of nanoseconds going into an appropriately small container seems likely. For example, a 62.5MHz counter going into 53 bits breaks at the same limit. Why 53 bits? That's where things start to get weird with IEEE doubles - adding 1 no longer fits into the mantissa and the number doesn't change. So maybe someone was doing a bit of fp math to figure out the time or schedule a next event? Anyway, very likely some kind of clock math that wrapped or saturated and broke a fundamental assumption.