Thank's a LOT Pcmoor. This a great help for me. I feel more "normal" and not so alone... I will take method 2. So if I understood well, I must rebuilt everything... No "magic" trick to eliminate old scaling of groups, and let the geometry like it appears without this "memory". Groups keep "memory" although one make them unique...!
As there is no mirror copy, the only way i found is to apply a scale -1 in X or Y axe.
In my project, i have a lot of components that are symmetricals and I've build all my models using this scale -1, without knowing this little "detail"...
Last, When you say groups "CAN" retain, and "scaling can easily become out of sync", is it unpredictable? or is there any ley, here? Sorry to insist, but i really like to understand and avoid future problems!!!
Really very grateful for your support and help.
Xtian

I'm dealing since meses with erratic behaviour of DC. I'ts hard to explain because it's not regular, and I've yet ask for this problem en december. Anssi told me about a Trimble bug when working en decimal centimetros that suddenly turns internally en inches. Really i feel desperate because there is no way to avance in my work: To resume, if i create a DC that contains 2 elements that i need to hide one or the other, it works still i put a button inside that send ON CLICK to change the value of the variable that hide or unhide one of the sub component.
Suddenly the component begin to change (scale X or Y or Z or both) alone, a little boit every time i click.
And finish to turn so big that the file crash. and there is no Ctrl-Z that works.
The same happend when I use the options menu to let the user to choose a value for the variable. It works, but if i make a new component that contains two, respecting the correct way (parent!XXX) to invoke the changes of variable, the same happens.
I'tried everithing, explode and rebuilt from scratch. NO WAY.
I put a file (DC BUG ERRATIC SCALE) from SKETCHUP 2021, whith 3 steps of the construction
(1): just the 2 originals DC
(2): the 2 same DC (made uniques)DC in one DC whith menu to change values
(3): the same DC that (2), just changing the origin and with a buton with ONCLIC.
Please just try to clic on (2) and (3), and let me know what happens, even if it's work (maybe it's my system -windows10,GPU QuadroRTX-Sketchup2021).
Thank's to anyone that can help me.
Christian Godard, Arquitect, Chile.

DC BUG ERRATIC SCALE.skp

HELLO TIG
Thank's a lot for your time and very usefull explaination and tool that work increible...!
I had to desinstall WINRAR for that to it stop to try to open the JAR file because it was no other option de asociation until... I realized that no JAVA was installed on my computer!!!
Now it's made and everything works perfect.
Thank's again and to Dave that helps me too.
Christian

I've installed the plug in SKM Tool de TIG and when I try to use it, something strange happens: I select an image PNG and use ImageTrimmer in Tools menu, and suddenly it open EdgeDetector.jar whith the RAR applicationR that show a file EdgeDetector.class and a carpet META-INF, and...that's all, folk's..!!!
It' everithing correctly installed (SKMTool in plugin folder), and in the Ruby Console something like ...:

Error: #<Errno::ENOENT: No such file or directory @ rb_sysopen - C:\SK\ALIS\CACHA\ARRIENDA\PIEZA\TrimmedImages\10JORGE[Edges].dat>
C:/Users/xtian/AppData/Roaming/SketchUp/SketchUp 2020/SketchUp/Plugins/SKMtools/ImageTrimmer.rb:277:in readlines' C:/Users/xtian/AppData/Roaming/SketchUp/SketchUp 2020/SketchUp/Plugins/SKMtools/ImageTrimmer.rb:277:in make_edges'
C:/Users/xtian/AppData/Roaming/SketchUp/SketchUp 2020/SketchUp/Plugins/SKMtools/ImageTrimmer.rb:201:in process_image' C:/Users/xtian/AppData/Roaming/SketchUp/SketchUp 2020/SketchUp/Plugins/SKMtools/ImageTrimmer.rb:170:in initialize'
C:/Users/xtian/AppData/Roaming/SketchUp/SketchUp 2020/SketchUp/Plugins/SKMtools/ImageTrimmer.rb:834:in new' C:/Users/xtian/AppData/Roaming/SketchUp/SketchUp 2020/SketchUp/Plugins/SKMtools/ImageTrimmer.rb:834:in block in <top (required)>'

...appears.

What is wrong?
Sorry to insist, but it was so promissing...! and I really need that fantastic tool. Is this a problem of directory name ? like what appens whith dynamic component when you're working in C:user...?

The image was only to show that the scene is 3D, not images. I add to this post a SKP of the scene, which comes whith the sketchy style and the flat model of the person whithe PNG material. Hope you can try and see that when you move the camera, the sketchy style sometimes don't apply until you stop to move it, and you clearly see that the sketchy style apply after the scene y rendered, so "cover" the image of the person... Try to see each scene to experiment what I try to explain.
Thank's.
This is a work for a show that we are still working on, so it's better if it's possible not to spread it much.
Thank's
Christian

Yes the window, the walls and all the furnitures are in 3D.
it seems "twisted" because the model is deformed vertex and face, and the sketchy style increase the sensation. Te character en photo is just a map on a rectangle of a PNG whithout bedge.
I'll send another image to show. The building beside the window are NOT 3D, just a drawing.

Hola: I've defined a sketchy style for lines that work great for my need, but when I put an object whose material is a PNG photo (that allow me to include a person whithout need to cut his exact outline), It seem that the sketchy lines are drawn AFTER the objet whith PNG texture. The problem is that this object seem to be transparent on the sketchy lines.
Is there any solution for that?