Deleting an activity having subactivities (phase) fails

Hello,
I noticed this bug a few versions ago but only reports it now as it is pretty annoying when having to delete activities.
To reproduce : go to "Activities" screen, and choose an activity that has at least one subactivity.
Try to delete the (parent) activity :
- a window asks for confirmation : click OK
- A second window asks for confirmation that the children activities will also be deleted : click OK
Then, a tooltip appears saying that nothing needs to be done for this activity and the activity does not get deleted.
A second bug of similar nature about deleting an activity having assignations has also be filed.

Hello,
Yes, reproduced on demo as well (connected as "gestionnaire", and using both Firefox (v33, but not v47) & internet explorer v11).
Please note that I got messages from time to time complaining about my network connection quality...

To be more accurate to reproduce on demo :
connect using "gestionnaire",
select first project in the list (ABC_vente)
try to delete activity #111 (which has activity #112 as child)
==> acknowledge first confirmation message to delete the activity
==> acknowledge second confirmation message to recursively delete the subactivity
you're done : message "Aucune modification à sauver pour l'élément Activité #111" appears and nothing gets deleted.
I will do screenshots if needed