I think this highlights the need for specific route planning.
I took specific care to guide along easy to follow routes with backstops, identifiers, short legs, and good links.
It's not necc how I would have run the course, but it allowed specific checkin at each control.
The worst was guiding across the "big swampish" area - twice. The first tme my guidee's apparently drifted left and when I outlined the hill they should encounter on the other side, they were to one side when I thought they were on the other. This ended when they saw "the flag" and proclaimed they were at 10, not 1 (!)
But I knew where they were, and except for an over and back to 1 (that was close), it was aok. Coming back, they drifted a bit again, but had good eyes to spot the control near the pond (by the small building). I had tried to use the creek to catch them in that direction.
The "worst" sort of directions would be to allow your people to miss the control and just keep wandering off into nondescript terrain...-)
I guess that does indicate - you need to gauge how far they have gone over time, and if their rate of speed changes, errors creep in.
Definitely route planning to avoid losing contact with the map makes a lot of sense!
I think the "B" section was easier in that regard, based on there being a lot of trails, and also some nice distinct contour features. "A" was tougher because it was less trail based, and also there were large areas that were pretty flat.