I have a lot of experience with those old cascade doors so allow me to answer. Based on what I see in this photo the top "louver" is missing and the louvers are slightly open.
The #3 engine is not in reverse because the cascade assembly is stowed. Remember this is a pneumatic thrust vectoring system and louver chatter or partially open partitions is not uncommon. There seems to be a pneumatic leak in the system allowing the louver doors not to stow properly.
The reason for this is a bad shuttle valve spring mechanism or people are injecting penetrating oil into the system or both. This penetrating oil makes the system function great for about 1 week, then it begins to gum up and the system will not function correctly. A common fix in a line maintenance environment and makes problems go away for a quick dispatch but this is not an approved maintenance practice.
I haven't seen one of these operate with one of the "Venetian blinds" missing expect by Kalitta and they’re a Mutha-F**er to change. In fact Cascade assemblies are so hard to change while at ABX
we had stations dedicated to doing this task, with extra training and tooling. The system is entirely inefficient; they weigh a ton, break down about every other trip and constantly will not go into interlock and have lots and lots of pneumatic leaks.