staceppa on "[Plugin: Visual Form Builder] Form submission hangs"

Hi
i have installed your plugin which i like a lot.
The problem i have is that whenever i try to submit data using the form the submission hangs, the server goes in timeout and for few minutes (up to 5) the website does not respond.
After those 5 minutes the site is back up and running smoothly.
This happens ONLY when i submit data using the created form.
Can you help somehow?
Regards

https://wordpress.org/plugins/visual-form-builder/