Paintings in structure blocks not loading in same place

This bug is very damaging. Structure blocks finally allowed us to clone entity's with structures, but now this bug prevents us from cloning large paintings, as they move.
I have made the same observation as Marcono in that that the paintings bottom left corner gets placed where the center originally was. Please fix this soon; my current projects involve cloning custom houses (including paintings) into various environments and it just isn't possible because of this. There is no work around.

I have a similar issue happening in 1.12.2.

Paintings that are 1x1 or 1x2 (wide x tall) are loaded fine, but 2x2 and up all load one block up from where they should be.

I've tested it with multiple paintings facing all directions, and anything bigger than 1x2 gets shifted up by one block.

Someone please check if that's still an issue in 1.13 or 18w30b.

Well, whether or not it was fixed, it's happening again in 19w06a.

This is in snapshot 19w12b.

The structure block attempted to load all the 4x4 paintings one block too high, and they got bumped. the 1x2 loaded a block higher, on top of a redstone torch. the 3x4 loaded correctly. 

Confirmed in 1.16.1 and 20w27a.

This is still evident in 20w45a, the issue appears to be that the correct attachment position is only saved to the blockPos tag in the structure's nbt file, and not the normal pos tag. The blockPos tag is never used to load the entity, only the pos tag, thus paintings are always spawned in the incorrect location.

Confirming this is still an issue in 1.17. 

I exported a house which included numerous paintings and other entities.  I made sure to include entities when using the structure block.

Expected Result:  Paintings are mounted in same spot as original.

Actual Result:  Paintings are shifted one block up, or unmount themselves as they won't fit in the spaces.

Still in 1.19

can confirm in 1.19.4

Confirm in 1.20.1

Confirmed in 1.20.4

Potential Solution?
In StructureTemplate#placeEntities before Mob#finalizeSpawn, it might be possible to run some kind of structure placement validation check which corrects the positioning of the entity (and any future entities that may have a similar issue?) prior to finalization.

By converting the painting variant's width and height to block sizes (Variant#getWidth() / 16), if the height is even, offset the painting Y block pos down by 1. If the width is even, and the painting direction is west or south, offset by Direction#getClockwise().getNormal(), then set the painting pos to that position.

The mixin code I wrote to test this solution (in 1.20.2) looks like this: (MojMap)

@Mixin(StructureTemplate.class)
public class StructureTemplateMixin {
    // Injects into StructureTemplate#placeEntities, inside the lambda of createEntityIgnoreException
    @Inject(method = "method_17917", at = @At(value = "INVOKE", target = "Lnet/minecraft/world/entity/Entity;moveTo(DDDFF)V", shift = At.Shift.AFTER))
    private static void fixPaintingPlacement(Rotation rotation, Mirror mirror, Vec3 vec3, boolean bl, ServerLevelAccessor level, CompoundTag tag, Entity entity, CallbackInfo ci) {
        if (!(entity instanceof Painting painting)) {
            return;
        }

        var pos = new BlockPos.MutableBlockPos();
        pos.set(painting.getPos());
        var variant = painting.getVariant().value();

        var width = variant.getWidth() / 16;
        var height = variant.getHeight() / 16;
        var direction = painting.getDirection();

        // paintings with an even height seem to always be moved upwards...
        if (height % 2 == 0) {
            pos.move(0, -1, 0);
        }

        // paintings with an even width seem to be moved in the clockwise direction of their facing direction,
        // if they're west or south.
        if (width % 2 == 0 && (direction == Direction.WEST || direction == Direction.SOUTH)) {
            var moveTo = direction.getClockWise().getNormal();
            pos.move(moveTo);
        }

        painting.setPos(pos.getCenter());
    }
}