First, check if you actually have two door entites:
- Select a single brush of the first door and press the L-key to open the Entities List.
If you open your map, you should find a highlighted func_door. Click on that
func_door node, only the brushes belonging to that door are now be selected.
Repeat this for the other door as well. You should have at least two func_doors
in your Entity List.
Check the settings for each door:
- Select a single brush from the door and press the N-key.
If the door has a "team" key, make sure it has a different team name. Doors with the same
"team" key will always open and close together.
- If the door has a "targetname" key, make sure it is different from the targetname of the
other doors (as far as i know, doors with the same targetname will also open together if
either of them is triggered)
- To copy doors: select the original door, press CTRL+C. Press ESC to deselect. Press CTRL+V
to paste a new door. This also works in other cases where you want to create new entities.