Hi, I've noticed this bug with large crumbled buildings cover that are present in ruined city type maps, this kind of covers once destroyed disappears normally as any other cover but still block movement. 

In some areas with a lot of this covers, once all have been destroyed they created an invisible wall maze that made navigate the map a nightmare.

 it can be easy reproduced in the two Viper's Nest missions that take place in the city maps.