This has happened to me a couple of times so far. It only happens after I add a bunch of static meshes and then run the PIE. Everyone blows up except me and the FPS drops from 45-50 fps to 5 fps. I've tried to fix it by re-building everything and/or closing the editor and re-starting it. Generally this fixes the problem but I always come back to a lower frame rate. I thought it might be memory related and have shrunken the LightmassImportanceVolume but I still get lower frame rates than I get on a full 64-person server. I've followed Yoshiro's recommendations on performance settings for the terrain but haven't messed with LOD's for my static meshes.
Just to give more detail, I only have about 300 objects (static meshes, destructables and 1 dominant directional light) in the map right now and terrain measures 64 x 64 x 256
Just to give more detail, I only have about 300 objects (static meshes, destructables and 1 dominant directional light) in the map right now and terrain measures 64 x 64 x 256