Not sure if this is a bug or not, or whether it is intentional, but the flaps lever for the Otter works the "wrong" way. You have to pull it to drop the lever, and vice versa. Furthermore the lever only has two settings, up, middle and down, which doesn't correspond to how the otter works IRL. The lever should be up or down, and each pump of the yellow handle either raises or lowers the flaps according to the lever selection. Otters have analogue flap settings, the workaround used in other sims is to have many smaller increments. If you can get the pump handle working in combination with the lever, this would be a very realistic way of working the otter.
On top of this, the indicator mounted on the dashboard only shows a slight change in the movement of the flaps, so it is impossible to read if you have one notch or two. I guess this is all linked.