Does Unity's Texture packer work in Tight packing and rotation mode, on Unity 5.6

I'm working on a game with a lot of large sprites... they are already packed into texture sheets using UNity's built-in packing. They all have transparency.

Using Unity 5.6.3p3 with new Ui

We need to save some memory / build size, so enabled tight packing, with rotation on.... I want the sprites to pack closely... overlapping transparent areas.... but... ...but now a bunch of the sprites appear in-correct in game... upside down, rotated, and/or the UV's in the wrong place, showing parts of the wrong sprites on the image.

Is this a bug in Unity?

Also looked at "Texture Packer" on the asset store.... in TP docs... it also mentions near the start...."Note: trim, crop, rotation is not supported for 3D objects and new Unity UI"

So is this broken, in 5.6? and is there any solution that works with tight packing and rotation (with new unity Ui)? if not, whats the next best backing option that does work ?

Thanks for any help in advance.