Hi!
I've found that sometimes Kontact's main toolbar is messed up and ordered backwards (please check attached images).
Other times buttons added by me just disappears when after quiting and launching Kontact again - albeit this just happened twice 'in a heck of long time'.

Reproducible: Sometimes

Steps to Reproduce:
1. Accommodate the toolbars as shown in the attached pictures.
2. Add or remove buttons to any other toolbar than the main one.
3.
Actual Results:  
Sometimes, too often, the main toolbar buttons order will be reversed.

Expected Results:  
Nothing more than the toolbar that I'm customizing is changed.