I suspect it was a morale issue related to my cavalry brigade. The Austrian infantry and cavalry pretty stupidly decided to attack, piece-meal and uphill. This was particularly foolish on the part of the Austrian cav, since there was perfect, flat cavalry terrain on my left, and a cavalry flanking movement there would have rolled up my line and enabled them to just march along the ridge and grab all of the high-ground objectives. Meanwhile, the Austrian infantry insisted on moving in brigade columns against a grand battery of my guns, getting one regiment after another wrecked and routed. The morale bar was about 75% in the Prussians favor. One Prussian brigade was a little roughed up on the morale front though, having been bruised in some melee fighting against Austrian infantry on my left.
Again, an Austrian cavalry charge there would have made all the sense in the world.
The Austrians finally got some guns set up and commenced firing on advancing Prussian infantry. The guns were entirely oriented to the WSW and W, firing into the flank/rear of a Prussian brigade advancing S of them to the W. Another Prussian brigade was located S of the Austrian guns, moving N toward them, in cover (forest).
I moved my cavalry brigade along a depression to the E of the Austrian guns, from S to N. Note that the Austrian guns were also at this point under fire by the Prussian batteries. I moved the cavalry up to the E of the Austrian batteries. These batteries were then able to spin 180 degrees, very quickly, and take my cavalry under fire. I ordered a charge, but the cavalry apparently decided that was a great time for an order delay, and sat there with their little clocks going. Meanwhile, the front two regiments eventually routed...toward the guns. The remaining two regiments must have been out of LOS from the guns, or at least one was, because it was getting shot at. The two routed cav regiments seem to have precipitated the morale plunge for the army as a whole, despite the Prussian infantry chasing literally all of the remaining Austrians off to the W and N. At that point I got the notification that I'd been defeated.
Even more oddly, this was the second time for this battle. I'd fought it once before, was apparently defeated, but when I returned to the strategic map I was able to click on the battle notification and it was like I'd stepped into a time machine...