Hi tullio0106,
Thank you for contacting us!
I have tested the smart-multiline-text-box component in Firefox as well but still I was unable to reproduce the issue that you do.
However when you disable the ‘height: auto’ styles the component has more than 10 rows which I think is not the functionality you want to achieve.
If we are to be able to give you proper support it will be best to share a code example of your case because this behavior could be coming not from the component itself.
Please, do not hesitate to contact us if you have any additional questions.
Best regards,
Yavor Dashev
Smart UI Team