V1.7 Problems with Prestashop 1.7.6.5 and keywords

[Pippo81]

Hi, i have a problem with keywords on index page.
After put 10 keywords when insert next keyword the site give me this error:
Si è verificato un errore inaspettato. [PrestaShop\PrestaShop\Core\Domain\Meta\Exception\CannotEditMetaException codice 0]
Can you help me??

Thanks