Thanks, Fredo.
I am working around this "issue" by unsetting the 'projected' flag from the appropriate faces prior to shearing with FredoScale. As can be seen in the SKP file I uploaded, FredoScale by itself does what I expected and projecting was unnecessary.

Thanks for the quick reply, Fredo!
That model I used for the screenshot I no longer have, it was just something I put together quickly to illustrate. I just made another one, hopefully more explaining.
As for my model, never mind it. I use a program for online backup and sync'ing across computers and it turns out it stores previous versions of files as well.

Attached to this post goes a SKP file. It shows a similar operation performed on a pair of boxes, the one on the right having projected textures. Along the green axis different techniques with and without FredoScale are used, and the differences are shown.

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boxes.skp

Hi everybody, specially Fredo!
I'm not sure if this is the right place, but I think I found a bug in FredoScale and would like to report it. Here are the steps to reproduce it:

1. I've drawn 2 boxes. Each is an individual component. The one in the right has the top texture set to 'projected', the left one does not.

2. Using planar shearing, I 'shear-ed' both along the blue axis, by the same amount.

3. I opened the right component for editing. Just opened, did not even click on a single surface. Texture placement gets messed up.

4. After closing the component it's easier to spot the difference between both textures:

5. Even after undo'ing the operation, textures are still incorrect:

The same effect happens if the boxes are not components, but with slightly different characteristics: if each box is sheared individually, only the one with the projected textures is 'damaged'. But if both are selected at the same time and the shearing is done to the whole lot, both end up correct, even though textures are set to projected in only one.

I first noticed this effect in a model I am working on, but the problem seems more serious there. After opening the component textures are messed up, and show in different ways if a component is open or closed:

In this case I can't even repair the problem manually. I do have a hidden rectangle with the whole texture, from which I can pick the texture and paint the new created geometry, but the textures never show up correctly, it does not matter if set to projected or not. I wish I had made at least a daily backup...