Around 3:40 you set up a waypoint tactic "Defend" for CO/A. When running the exercise it would NOT behave like "Defend" is described in Chapter 8, but default to "Hold" behavior because there is no unconditioned retreat route specified. If a route is a dead end, the only option for a unit is to stay in this position until the bitter end.
If you want them to react intelligently to incoming fire, you must have some sort of an escape plan - that is, an unconditioned route leading away from the untenable position if you want to rely on the implicit embark conditions that Steel Beasts has built in, or you need to set up one or more conditioned routes with contingency plans for incoming direct and indirect fire.
Then there's the meta critique. You have the CO move alone with any form of protection or backup through a forest, across a stream (where in real life you wouldn't know whether it could be crossed at all), then across a railroad embankment (which in real life has pretty steep flanks of approximately 45...50% inclination, very close to the limit of 60% for most tracked military vehicles under optimal conditions of traction). This doesn't play a role in SB yet because the terrain is artificially simple to traverse, but I bet that in real life the by far simpler solution would have been for the CO to break off at waypoint three and take the road across the rail line a bit further to the west of the current crossing point. That is, if you still want to send out the CO to his very lonely position.
Of course you're in control of your own scenario, so you know that there won't be a flank threat from the northern river embankment where the CO would be really, terribly exposed. But would you risk that in real life?