When you use sweep with an mesh that has multiple collision primitives only one is used for the sweep test.
affected versions: 4.21 and 4.21.1
works as expected in 4.20.3 and below
This bug is very anoying as we rely on correct sweep detection, because we have a lot of objects with multiple collsion primitives which now we spawn inside of walls.
just take one static mesh and setup the simple collsion to use 2 box collision one for the upper half and one for the lower half.
Now create a blueprint actor which has this static mesh as root and add the blueprint node like in the screenshot
Place this acotor a bit floating over the ground and press play in editor
after 2 secs. the object will go halfway in the ground.
If its not working the first time swap the locaion of both collision primitives in the static mesh, as this time the right one was on the bottom.
If you need a simple project to reproduce it please let me know.