Okay, I got 0.9.7 out the door, now it's time to look at this.
Grouped pieces move on ungrouping: This happens when the group was mirrored/rotated. The move on ungrouping is confusing and I should fix it. Might be hard to fix perfectly, but we'll see.
Editor groups even if no groups defined in the level: This is backwards compatibility with C++ Lix and early D Lix levels. Line 93 in polar-pop.txt reads:
:matt/winter/06: 312 32 n
This n means no-overwrite: Draw (pixels of the piece annotated with n) where there is air in (the map rendered so far), but do not draw over solid pixels in (the map rendered so far). Since D Lix 0.4, we don't support no-overwrite anymore, but instead tile grouping. Both features allow the same map designs, and no-overwrite-designs are converted on level load to grouped designs.
The resulting group may be very large to guarantee the exact same looks of the old level design. It might be prudent to replace this single no-overwrite tile: Remove the n with a text editor, open the map in the level editor, and fix any strange looks.
Thanks for the reports!
-- Simon