@Flazz: Apart from what Khabal said, there is a command to select only the nearby units. So you go to a spot with stuck units, order nearby soldiers to follow you, and you relocate them accordingly. A bit tedious, but it usually solves such issues.
Also, don't forget that you can issue the 'hold position' order by holding down F1 and placing the flag where you want it to be. And when troops act weirdly when you order them to hold positions (they start retreating, moving elsewhere, or simply get stuck), as an alternative, you may use the 'Stand ground' order as well. There were some cases when it did wonders for me, whereas 'hold this position' failed hard.
Other than that, the AI parhfinding is known to be flawed in Warband in general...