One of my maps .uexp is extremely large

Hi!

I recently noticed that one of my maps generates an extremely large .uexp file, almost 500MB. Compared to the other maps it’s more than 10 times larger.

It contains few actors. A pretty large landscape, but other maps has bigger landscapes.

There’s a special static mesh that I suspect could be the problem. It is hidden in game and casts hidden shadow and far shadow, it covers the whole landscape to block out directional light as it is an underground dungeon (the map is a submap on a bigger world).

Any ideas what could cause the large file size?

Today I noticed that the landscape actor for this specific level has a MUCH larger number of instanced components.
It seems that if I create a large single landscape, that is one instance. Then if I use the add tool it keeps adding instances for each click
For this level I pretty much added all those quads as I as going, resulting in thousands of instances. Could that be generating this humongous .uexp file?

are you saying that your using a mesh to block the directional light? why would you do that? just delete the light

This is an underground part of the level. The directional light is the sunlight for the areas above ground.