AP Plummets After Crossing Don [1 Panzer Army Campaign]

[75Pak]

In the first scenario in the 1st Panzer Army campaign, my AP points plummet for 2-3 turns after I cross the Don.

I made a very aggressive advance on turn one, and penetrated Soviet lines in 5 separate locations, making their entire position along the Don completely untenable.

I suffer about 350 casualties but inflict about 3,700 casualties on them on turn 1 [July 25]. Their losses rise to slightly more than 10,000 by turn 2 [July 27], while things heated up and my losses are around 1,700 by the end of turn 2.

By turn 3 their losses are close to 15,000 while my losses stand at just shy of 2,500 but I have crossed the Don in force and their entire line has collapsed and I have begun pocketing small groups of their forces.

By turn 4 I have suffered losses of 3,750 but their losses are in excess of 21,000.

However, my AP grinds so low I am not able to do anything of consequence on turn 5 or turn 6.

August 2 and August 4 I have not been able to do anything of consequence, my forces are completely hamstrung, and I could easily have taken Metchetinskaya on August 2 and Proletarskaya on August 2 or August 4, but now I probably won't get the former until August 6 and the latter until August 8, and I won't make Salsk until August 10 or August 12, there goes my winning with 10 days to spare.

The road south was essentially completely open and for 2 key turns my forces had less than 50 AP and were not able to do anything of substance.

Why did this happen? Is this a bug?