Comment 1 for bug 1546531

Also affected by rev14655:
- 'Alt+LMB' to select under works only once, unless the top-most (?) object is modified again (which probably invalidates the cache).
- 'Alt+mousewheel scroll' to cycle through stacked objects hangs inkscape (AFAICT it's still ok with rev14653)

These other regressions are not limited to groups - let me know if you want separate reports for regressions related to stack order.