Dominik D
Regular
Whether you can stream assets on time depends on your camera speed. If this fly-through is faster than the expected player movement speed, you'll experience some popup. Another plausible reason are issues with world partition HLOD baking. Tooling for issues around WP isn't great (yet, hopefully) so occasionally some actors may be excluded from HLODs (you need to pay close attention to warnings and know how to troubleshot issues). But even if things are properly baked, it's possible that your streaming setup is tuned for the ground level line of sight and not a flyby.maybe because it still has to run on last gen hardware and you can't make a whole different looking game for gameplay purposes, plus the still available 120fps mode which uses the standard rendering.
It's also pretty important to use assets without scaling. Not only does this make texture density consistent (or at least allows you to manage it) but if you have a mesh that's supposed to be 20x20cm and set its smaller LOD to "disappear" (a valid thing to do) but then someone scales it to 2m x 2m because it still looks good up-close... The opposite can also be true (scaling assets down) and will tank your performance.