Added repro mission "27569_AiCantDoMoveInside1.Altis".
The issue seems to be location specific, rather than building model specific as results vary for different instances of the same building.
Repro:
Open mission in 2D mission editor.
Preview mission.
Select unit 2 (F2).
Point mouse at position 7 of the building in front of the player (the right edge of the balcony). See screenshot "CEEB_orderPosition.jpg".
Press Middle mouse button to order unit 2 to move to that position.
Watch the unit successfully reach the position. Note the on screen hint showing the unit's expected destination isEqual to the return of the building pos. When the AI arrives, he reports "ready" or "standing by".
Restart mission (or just order the unit to return to the street next to you).
Use the custom action to order the unit to attempt to commandMove to the position. Again, the unit's expected destination isEqual to the return of the building pos.
Watch the AI unit move to the ground level underneath the actual position, then stop. Note the AI reports "ready" or "standing by" and the return value of moveToFailed remains false.
10 (Optional). Order AI to the intended position again with F2 + MMB. Watch them succeed.
This repro is one of many examples that are found using the "AI_VS_Buildings_R1.Altis" test mission I added to #4553. Script AI fail to reach the destination, but player can successfully order his subordinate units to move to the same position.
I have not investigated using waypoints to achieve the same result.