Ok think I nailed it. Several vehicles in the WAW20 technics.ini do not have FireFastTargets set to 1
They include:
BA_64
FAIM
LVT_2
M8_Greyhound
HoRo_MG
Tatra_OA30
Nimrod
Sdkfz251
DemagFlak
SdKfz6Flak37
OpelBlitzMaultierAA
ZIS5_AA
MaximeGaz
M3A1_APC
M16
M16_US
3 of the vehicles are in my test mission and the Demag and SdKfz251 are in the Black Death track.
Seems to be fixed now that I've added FireFastTargets 1
Edit: looks like the technics.ini entries are the same (at least for the demagflak) all the way back to the initial release of CUP. Has the default Car class behaviour changed from a default of shooting at aircraft to a default of ignoring them unless FireFastTargets 1? I'm pretty sure I remember initial troubles in the black death track after CUP's release with the tracers freezing.
From what I think to give more historically correct behaviour:
BA_64 - No AAA capacity (Armoured car with small MG and cramped turret)
FAIM - No AAA capacity (Old Armoured car with small MG and closed turret)
LVT_2 - No AAA capacity (side MG suited for ground troop support)
M8_Greyhound - No AAA capacity (Armoured car with small AT gun and coaxial MG)
HoRo_MG - No AAA capacity
Tatra_OA30 - No AAA capacity
Nimrod - Correct AAA capacity
Sdkfz251 - No AAA capacity
DemagFlak - Correct AAA capacity
SdKfz6Flak37 - Correct AAA capacity
OpelBlitzMaultierAA - Correct AAA capacity
ZIS5_AA - Correct AAA capacity
MaximeGaz - Correct AAA capacity
M3A1_APC - No AAA capacity
M16 - Correct AAA capacity
M16_US - Correct AAA capacity