Obscene amount of lag, and invisible walls of destruction.

[YaBoyShredderson]

I have a bug that makes the game entirel unplayable. Ok so when i go to the mun, the closer i get, the more laggy it gets, and when i try to land, the altimeter at the top breaks around 2.5km above the surface, it just says 1, but mechjeb is fine so i continue. But about 20m above the surface, i just explode? I have all the indestructible cheats on and it still happens, i try minmus and duna and it still happens. On minmus and duna i also went through the ground amd exploded about 10m BELOW the surface.

Whats going on? I thought it astronomers visual pack causing the lag, and the lag causing the bugs, but nope. I removed it along with eve and scatterer and its still just as laggy. The only other thing maybe is sigma dimensions. Im using 6.4x size with 9.6x distance, 0.3 terrain. Ive had this isse before with no way to solve it and wasnt using sigma then so i dont think its that either.

Im using ksp 1.8.1, i have a ryzen 5 2600, a 2070 super, and 16gb 3200mhz ram.

[Entropian]