Beware that what you call your “pool pilot” (likely similar to my own PoolCop) measures water temperature at a different place from your remote DS18B20. Upper and lower layers of water in a swimming pool may have significant temperature differences , especially when the pump is not working.
Also, I would replace the FGK-101 battery before tinkering with your remote DS18B20 : strange things happen when the battery comes near its end of life.
Anyway, the proper check would be to compare the behavior of the FGK-101 fitted with a NON-remote DS18B20, and a “calibrated” thermometer within 10" of each other.
Then you will know for sure if your remote DS18B20 is defective (which according to some posts in this thread seems to occur even more frequently than for “naked” DS18B20).
And for the sake of completeness, yes, you could customize my custom Handler and “skew” the measured temperature before it is reported by the Hub. But I do not recommend you go this way, since the temperature difference is too big to be only a minor adjustment problem.