Both Pioneer 10 and its sister probe Pioneer 11 have gone more slowly than they should - it's a teensy, but measurable, amount of slowing that couldn't be accounted for. It's spawned all sorts of explanatory theories, many of them quite daft.
Finally, someone searched out the old data, which is in formats no longer in use. So that meant finding old equipment to play them and then transferring the data to a current format in order to analyze it.
When they did, they finally concluded that the miniscule slowing resulted from the heat radiation of the probes pushing against them and slowing them down. So probably no new exotic physics and no aliens involved.
More detail at Mystery Tug on Pioneer 10 and 11