Keyboard letter 'B' sometimes does not work

Hello,

The letter 'B' sometimes does not work (iPhone X).

Already done :

• Kill all apps
• Restart Iphone
• Delete all settings an restart

Sometimes, after kill all apps, the 'B' works again.

Sometimes, after restart, the 'B' works again.

But now, don't work after actions bellow.

After deleting all settings an restart, does not work anymore. But work again after some hours.

But now, does not work again (after hours) !

Does not work in message, mail, Wattsapp, Etc.

Please help !

Thank you very much.

Nelly