Thanks for the ideas superdreamgen.
I have experienced bug UE-53053 as well, but only if i try adding instances before everything is fully loaded in.
I’m not changing the transforms of any of the instances, so it can’t be that.
I did look at the transforms of the blocks that showed in removalIndexes2. It’s interesting that removalIndexes usually had dozens of values, and removalIndexes2 only had 1 or 2. The transforms of the blocks in removalIndexes2 were also in removalIndexes.
I think the most likely cause is that GetInstancesOverlappingSphere is giving me the wrong indexes, or they are changing right after I call it.
I have not yet tried using any other trace methods. I’ll look into that later, but first I’m going to try detect if those index values are changing during my function.