Norway's Halvor Egner Granerud won Sunday's competition, producing jumps of 140 and 142 metres and earning 6.4 points more than second-placed Anže Lanišek of Slovenia and 9.3 more than Kubacki.
Another Pole, Piotr Żyła, finished sixth in Ga-Pa, while compatriot Kamil Stoch, a three-time overall Four Hills champion, claimed ninth place.
Granerud, who also won the opening event in Oberstdorf, Germany, ahead of Żyła and Kubacki, has now opened up a comfortable lead in the overall standings.
Meanwhile, Kubacki is second overall, with Żyła sitting third, news outlets reported.
The Four Hills Tournament, which is part of the ski-jumping World Cup circuit, features a series of four competitions taking place in Germany and Austria every year.
Following the contests at Oberstdorf and Ga-Pa, the series will move to Austria for events in Innsbruck on January 4 and Bischofshofen on January 6.
Poland's Stoch, a three-time Olympic champion, won the 2020/2021 season's Four Hills Tournament and also triumphed at the 2017/2018 and 2016/2017 tournaments.
Meanwhile, Poland's Kubacki, who leads this season’s World Cup standings, claimed the overall Four Hills Tournament title in the 2019/2020 season.
Dawid Kubacki Photo: PAP/EPA/CHRISTIAN BRUNA
The 2022/2023 ski-jumping World Cup circuit, run by the International Ski Federation (FIS), features a total of 39 competitions, including 32 individual events, in various countries.
Austrian Thomas Thurnbichler this year took over as the head coach of the Polish men’s ski-jumping team to replace Czech Michal Doležal.
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Source: TVP Sport, PAP, vierschanzentournee.com/en