As mentioned in the video the trigger that decides whether you can drop the cargo or not is not working properly because this mission was created for the old caucasus map that had different terain data. If you wan't to complete the mission and this trigger to work you need to go to the mission editor , find the trigger and increase the AGL altitude requirement. By default it's too low forcing you to land on trees. Increase it to something like 1 or 2 thousand feet and it should work just fine.
As mentioned in the video the trigger that decides whether you can drop the cargo or not is not working properly because this mission was created for the old caucasus map that had different terain data.
If you wan't to complete the mission and this trigger to work you need to go to the mission editor , find the trigger and increase the AGL altitude requirement. By default it's too low forcing you to land on trees. Increase it to something like 1 or 2 thousand feet and it should work just fine.