I thunk i ran into a issue : plasma 5.3.2 (ubuntu 15.04) with backports activated because i keep having crash with my intel driver i guess.
When i create / update a new custom global shortcut, it is not applied when i click on the apply button.

I have to first create another dummy global shortcut so the previous one will work. This is kind of frustrating, i don't know if this was found or already fixed.
Where should i report this ?

I wonder if it's an issue in kglobalaccel, or in the shortcut configuration. IIRC, I haven't seen it in the latest dev branch for a while (just tested), though. What steps are you doing when the problem manifests?