Hi @Jessy5765 - i’m coming back now to the project that uses this, and I’ve managed to put in a workaround. If you use the “Grass” node in your landscape material node to place grass, rather than manual placement with the foliage tool, then the grass will appear near instantly every time.
Whatever the issue is, it only happens with manually placed foliage that is placed with the foliage tool (tested on latest 4.23.0) and is a direct function of the amount of foliage in the area - basically meaning that if I just place a small copse of 30 trees they’ll appear almost instantly, same time as the grass, whereas if I try to add an entire forest of trees, the same problem will persist.
I did log a request many years ago on answerhub, but Epic couldn’t reproduce. Looking at it and thinking logically, it is probably because the kite demo they tested under used the grass node to place the grass? (this is just a guess, i have to actually take a look and see!) so they wouldn’t see a problem.
In the long run though, using the Grass node is far superior as nobody has time to be manually splatting foliage all over their world with a painting tool.
Hope this helps someone!