I've seen this mentioned in passing in other threads, but I haven't been able to find a specific bug report regarding this issue in particular that I'm coming across with complex layering of graphic elements.
I've got an example of what's happening on my attachment. I created a graphical widget for keeping track of time and days my PCs will spend on a cross-country trek (time sensitive module). Everything is left ungrouped because I still need the clock hand and the night/day panel to be manually rotated and the text field accessible. The layering of elements should be as follows:
*Front*
Clock Hand png
Day Tally Text Field
Clock Dashboard png
Day/Night Panel png
The Overmap png
*Back*
In the attached file, the first image is what the widget is suppose to look like, and the second and third image display the z-layering snafu that happened when I switch pages.
When the page is reloaded, the elements' z-layering gets rearranged. The map sometimes gets filed to the front. The text field sometimes gets shuffled to the very back. The day and night panel often pops above the dash. Etc.
The reshuffle also happens if I grab all the elements of the widget and move it without holding down alt - the snapping almost always makes the day/night panel pop to the front for instance. Oddly enough this happens even when I have the grid deactivated on the page. The only way I can retain the z-layering is by moving while holding down the alt key.
Windows 7
Chrome 19.0.1084.52
Screen Resolution: 1366 x 768
Browser Size: 1366 x 610