WiFi problem on stock ROM topic

Hello all,

After testing CM12 and stock Lollipop ROM, i have decided to restaure stock ROM (NI4)
Everything works fine (and after few weeks on Lollipop, Kitkat is so ... smooth) , but i have a problem. Sometimes WiFi loose the connexion and it's not possible to reactivate the toogle ! WiFi stop and after is impossible to reactivate it ! The only solution is to activate airplane mode or reboot the device
What's wrong with it ? Do you have a solution for that ?

Thank's a lot in advance !