I've figured it out! The issue is that the TE_F9_S1_Tank part has a patch (Extra_B9Tanks.cfg) which adds a B9 fuel-switching module, but then CryoTanks adds another fuel-switching module because the TE_F9_S1_Tank has standalone LiquidFuel and Oxidizer resources (lines 39-50).  The fuel-switching module from CryoTanks has an addedMass variable defined, so the check in SMURFF.cfg line 1020 passes, but when SMURFF tries to grab that variable in line 1022, it looks in Tundra's fuel-switching pa
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