Dear @fr
It is difficult when working with Third-party plugins to know what exactly the problem is, In the past we have had difficulties with Contact form 7 but made a few compatibility updates since then, However there are always bugs that persist.
Is it please possible to update all plugins and Lay theme?
Maybe you have already tried this
Thank you for your patience and apologies that we do not have such a direct answer/solution.
We cannot guarantee that Lay Theme will work perfectly with other Third-party plugins.
Sincerely
Richard