Causality and the Warp do not mix:
"One particular example from one of the novels: in
Desert Warriors, a regiment of Imperial Guard is sent to a far-flung world to investigate the "mortis-cry" of an
astropath, which amounted to "Help, I'm dying!". Because
Hyperspace Is a Scary Place, where weird things happen, they arrive
before the signal is sent. The book's epilogue makes it clear that the distress signal they were sent to investigate is their own
"The most common way of FTL travels utilize a kind of hyperspace known as the Warp. It is a parallel dimension where there is no time as we understand it (so one can reach destination hundreds years into the future — or into the past), [...]"
"For bonus logical headaches, there's a story about accidental time-travelers who were responding to a distress signal (also sent through the Warp) from a ship that was surrounded by enemy vessels... when they popped out, the ship they were aiding was nowhere to be seen, but they were in the middle of an enemy fleet, so they sent out a distress signal..."
from TV Tropes.
Or they mix as well as lighter fuild and a spark.