When negative scaling is applied to an instance of an ISM, the instance transform is updated to apply a rotation instead. The same thing should happen when packing actors into ISMs for Packed-Level Actors.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-215779 in the post.
| 0 | 
| Component | UE - World Creation - Worldbuilding Tools - Level Instances | 
|---|---|
| Target Fix | 5.8 | 
| Created | May 24, 2024 | 
|---|---|
| Updated | Oct 17, 2025 |