@FMErwinRommel Good find! As in Global “UK Pacific units” simply do not exist.
By the rules “All combat moves, combat, and noncombat moves are made or conducted as any other power’s single, united force.”
So the TripleA battle calculator seems to somehow “sort” those units depending on whether they are on the European side of the map or on the Pacific side of the map.
Interestingly this does not occur with sea units. Those are correctly represented as being “British”, even on the Pacific side of the map.
In the attached savegame please use the BattleCalculator and look at SZ 37 and 39. The UK ships are correctly represented as “British”. The Infantry units in Malaya instead are incorrectly represented as “UK Pacific”, while they should be “British”, too. Switching to “British” sets everything to “Zero”. This is not exactly @FMErwinRommel 's scenario, but good enough to represent the issue.