Strange geometry popping up when using LODs

Hi everyone,

I recently started working with Unreal and I’m facing an issue when using LODs.
Since I’m importing a lot of static mashes with hundreds of thousands triangles, I wanted to improve my performance by using LODs. After creating a pretty basic LOD rule, unreal sometimes creates very strange geometry that definitely doesn’t belong to my imported CAD file.

Please see attached screenshots:

Is there a way to stop this annoying behavior?

Thanks a lot for your help!

Has anyone seen a similar behavior before?