Thanks for the blueprint Unfortunately this frame drop is caused by the physics engine, or more precisely, by too many small construction elements which are at the same location. It happens if the player collision shape collides with the construction elements (every construction element has its own collision shape).
Unfortunately there isn't much we can do about it currently... the current physics engine isn't thread-safe, that's basically the culprit. We had intentions to change the physics engine though, but this requires a lot of work. Maybe this will happen at a later stage