[BB1] Climbing issues - Bug or am I missing something?

Dell Inspiron 7577 Gaming Lapop with i7-7700

On various occasions now, I’ve had issues where the system won’t let me climb onto a roof. In the most recent Freiheit playthru, none of my squaddies could get onto the upper level of the Beacon Office to set off the beacon - it wouldn’t even let my Heavy Jetpack onto the roof.

At the same time, it did allow troopers to climb/jet onto the walls. So it seems as if when there is an option to enter a building rather than climb onto it, the system defaults to ‘enter’.

Am I missing something here? Is there a button to press like in XCOM where you tell the squaddie to go ‘up’ rather than ‘in’ - or is this actually a bug?