1. Place 2 or more vehicles in a group near some obstacles (buildings, rocks, poles, etc..).
2. Order the group to move somewhere with past the obstacles.
3. Observe as the leader successfully paths around while the subordinate vehicles get stuck on absolutely anything in their way.

The workaround to this is to never group vehicles, but this makes combined arms or mechanized squads very difficult to create without extensive scripting.

I was playing Arma 2 the other day and noticed how each AI vehicle tried to keep formation, but was able to temporarily break formation to path around obstacles.

If this issue is unfixable, at the very least it's something to keep in mind for Arma 4, as it makes mechanized squads impossible to create with AI in Arma 3.