Instances of an instanced static mesh component in BP not showing up

Summary

I am assembling a building in a blueprint from instanced static mesh components, and the 20th instance and more are not showing up in the level.

Please select what you are reporting on:

Unreal Editor for Fortnite

What Type of Bug are you experiencing?

Assets

Steps to Reproduce

I added 21 instances to an instanced static mesh component of a blueprint.
The last 2 don’t show up anymore.

Expected Result

I should be able to add many more instances, performance and memory limits permitted. The source mesh has 857 vertices and 3 1K textures and should be well within the requirements.
I asked the Epic AI and got the answer in the screenshot below, that, if correct, might give a clue, as it says that there is a 19 instanced static mesh components limit per blueprint, which oddly correlates with the only 19 instances showing up in my case.

Observed Result

More than 19 instances don’t show up in the level after compiling the blueprint.

Platform(s)

PC