There’s a new feature in UE 4.25 which lets us send an array of custom data per instance to the material. However, it doesn’t work reliably in hierarchical instanced static mesh (it works perfectly in ISM). Does anybody know what’s the problem? Or is there a workaround for it? Or is it a work-in-progress to bring it also to HISM?
Link to a what seems to be very related question:
Im having issues with it as well, it seems to break down around 150 instances and is progressivly worse the more you add
I saw it reported in 4.25 at least 5 times. Unreal Engine Issues and Bug Tracker (UE-92865) I also reported it in May.
For now the only alternative is using ISM instead of HISM. I hope this can be resolved in the future, because I cannot imagine my life without LOD 
is this resolved in 4.26 ?
Same question!