Caps lock won't work!

Does anyone experience the same?

My caps-lock function does not work.
It is correctly enabled in Settings. Everytime I double-click the Shift button, the key becomes blue-filled but still after the first letter it goes back to white (and no more capital letter).
I have to manually hold down the shift button for all the time I need it.

This as been the same also before the iOs update.
Any idea or advice?
Thanks,
F