Create two inclined belts that go from the ground level to the +1 level.
Connect the two belts with 5 sorters, one in each belt segment. The sorters thus slowly rise up from the ground to the +1 level, connecting belt segments that are at the same level. Useful trick, btw!
Make blueprint.
Build blueprint (either immediately, or copy it out, paste it back in again).
The newly placed sorters are all built on the ground level. The first two (ground, ground + a tiny bit) correctly link the belts. The other three do not. It appears that all blueprinted sorters are being built on the ground level.
Left to right: manually placed sorters, blueprint (immediate build), blueprint (copy out of game, paste back into game).
Replication steps:
The newly placed sorters are all built on the ground level. The first two (ground, ground + a tiny bit) correctly link the belts. The other three do not. It appears that all blueprinted sorters are being built on the ground level.
Left to right: manually placed sorters, blueprint (immediate build), blueprint (copy out of game, paste back into game).
Tested with all other mods disabled.