Extreme framerate drop while being around a spawner

After a fresh reload everything is OK like in Picture 2019-01-06_22.14.04.png

After being around a the Spider-Spawner for about 15-20 Minutes the Framerate drops to 1 FPS see 2019-01-06_22.36.28.png and the game gets laggy ...

• When I leave the Range of the Spawner ... The FPS gets normal and the Lag disappears
• When I reenter the Range of the Spawner ... The FPS gets back to very low
• When I close the game and restart it, the Effect is gone for another 15-20 Minutes see 2019-01-06_22.55.19.png

I have made also a Zip of the Saved Game to reproduce the effect if needed. (400MB)