You're at least partially right. They lost 4 knights earlier when a flaming pot crashed on them (from a catapult), that's why I ran them around the formations in the first place. After that they had 16 heroes left, and after circling they reformed into a double line, aligning perfectly. For some reason the siege didn't respond (no ballista fire), but the charge was bogged down by the siege equipment, and their retreat failed due to another (already destroyed) piece of artillery. It was unlucky, and for someone used to chase artillery off the fields with Steppe Cavalry, a shock as well.

Lost the battle, even though the last four knights did marvellous deeds of arms, that there was none did so well as them that day. And king Marino was wonderly wroth, and sent a host led by sir Balsamo Saunce Pité to meet the treacherous Polish...