Unreal Engine Issues and Bug Tracker (UE-109149)

Steps to Reproduce

Open/create a new empty project
Go to project setting and check 'Save LODActors to HLODPackages' and uncheck 'Invalidate HLOD Clusters on changes to the Sub Actors'.
Create a new empty level: Add some cubes next to each other which we will be merge to a hlod.
Enable 'Enable Hierarchical LODSystem' in World Settings and open the Hierarchical Lod outliner
Add an extra HLOD level so you have two HLOD levels. Click 'Rebuild all' to generate all hlods and 'Save all'.
Create a new empty level and add the previous map with the hlods to the current one via Levels -> Add Existing. Save all.
Open the map containing the hlods again and check the Hierarchical LOD outliner. The HLods are now broken: naming is wrong and some extra actors are suddenly added.

There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-109149 in the post.

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Fixed

Component	UE - World Creation - Worldbuilding Tools - HLOD
Affects Versions	4.26.1
Target Fix	4.26.2

Fix Commit	15499892
Release Commit	15499892

Persistent level containing sublevels with HLODS invalidate after saving.