Since version 1.5.0 of CopyInserters when highlighting for sorters that can't be built was added, sorters aren't placed when their position becomes valid after being marked as invalid. That's particularly troublesome for my style of building, which often involves placing a line of buildings until I reach a section of unfinished belts, then positioning the preview while waiting for the drones to build those belts. The placement validity seems to only update when the build preview is moved, so if it's positioned before belts or connected buildings are finished, it won't even try to place those sorters unless the cursor is moved somewhere else and back again after all connected stuff is finished.
Since version 1.5.0 of CopyInserters when highlighting for sorters that can't be built was added, sorters aren't placed when their position becomes valid after being marked as invalid. That's particularly troublesome for my style of building, which often involves placing a line of buildings until I reach a section of unfinished belts, then positioning the preview while waiting for the drones to build those belts. The placement validity seems to only update when the build preview is moved, so if it's positioned before belts or connected buildings are finished, it won't even try to place those sorters unless the cursor is moved somewhere else and back again after all connected stuff is finished.