Sorry for replying to this ancient report, but the bug is (sort of) still unfixed, though only with the maze it seems. I'm still unable to save scenery with OpenRCt2, but now instead of being offset, the dialogue claims it contains invalid scenery and placing it causes it to appear invisible and off screen. Loading a custom maze build in vanilla RCT2 will work, but will still place the scenery at a different position (looks like some sort of coordinate switchup) than in the draft.
You can try to replicate this by building one of the pre-made mazes like "Crazy Castle" and saving the build with all of its scenery and trying to place the new copy you just made. For me, this always results in what seems to be a maze with corrupted scenery data.
I'm using the current stable version v0.2.1 (8ac731e).