When i zoom in (change camera FOV) while outside the cull distance of a foliage, it does not reappear. I think this was the case before ue version 4.25 (or similar). Note the LOD does change when zooming in/out if camera is within the cull distance.
Found a similar issue where the material billboard size(screen size enabled) does not change(size should reduce) when zooming in. Not sure these issues are connected.