Inconsistent results when giving additional vehicle even if not required

Is it normal to have one result when specifying ONLY 1 vehicle available, and another order result when specifying more than one vehicle?

Reproduce the routing case with one available vehicle and then with multiple vehicles, comparing the returned order. Determine whether the differing results are expected for this vehicle-routing configuration, then document the cause and expected behavior or add a focused regression test if the behavior is confirmed.

Written by the indexing model from the issue text.