Field locked after wrong content

Hello! What a fantastic plugin. I have two contact form 7 on my frontpage.

The first one is only for letting visitor send their phone number.
The second is a normal contact page at bottom of page.

The second form works perfectly, but in the first one, if visitor for example types letters instead of numbers the form will not be accepted. After the message “please try again” pops up and disappear again the field is locked. Visitor cannot type or send again unless they reload (F5) webpage.

Any ideas?