This is the last of three (minor) screenset issues I've noticed. If you want to reproduce it, follow these steps:
 
1. Load the Normal project template.
2. Hide the MultiDock.
3. Enable Auto Track Zoom (View -> Auto Track Zoom).
4. Pack the two default tracks (if you don't see them, insert two tracks) into a track folder by selecting the tracks and clicking "Move to Folder" in the right-click menu.
5. Color-code the track strips (whatever color you like, just to make the issue easy to see).
6. Minimize the track folder (if not minimized).
7. Adjust the sizes of the current and non-current tracks like this:
(edit: i.e. make the non-current track slimmer than the current track)

8. Lock the current screenset (Main Screenset).
9. Switch to some other screenset.
10. Switch back to Main Screenset (which you have just locked).

[Expected Results]
The track folder is still minimized (because locked screensets are supposed to remember everything).
 
[Actual Results]
The size of the folder is changed to match that of the non-current track, like this:

 

Reported on Dec 6, 2013
Confirmed and submitted to development on Jan 4, 2014

Only way I could do this was to swap steps 6 and 7.
 
I notice in the screenshot you have a "User" preset, I don't have this so I set it to "All", is it reproducable under these conditions? Anyway I couldn't reproduce with X3D Producer so far?
 
Thanks

It was my mistake that I used the "User" preset (which I created myself) in the pic, but, yes, "All" or any other preset should be able to reproduce the issue. The point is that the non-current track needs to be slimmer than the current track, and the track folder needs to be even slimmer than the non-current track, before the screenset is locked.
 
You have to swap steps 6 and 7? Note that you can skip step 6 if the folder is already minimized.

> You have to swap steps 6 and 7?
Yes, if I followed step 6 the screenshot on step 7 would show a minimized folder rather than a folder with two tracks (maximized)?

Hmm...strange, before I posted I followed the steps and found no error in them. Anyway, it's ok as long as the image on step 7 is achieved. So, were you able to reproduce the issue?

Thanks Jlien
 
Steps 6 and 7 definitely need to be reversed.
 
Post #3 gave me the clue I was looking for (i.e. pay attention to the sizing, might be worth putting that in the steps).
 
So I tried to recreate the screenshot exactly, and I had to use the "Mix" preset to get rid of the FX bin (so that's an extra step).
 
So I can reproduce this with these revised steps - Cheers!

According to Jlien X not fixed in X3E.