Ajax form not working since grav-plugin-form 3.0.6-7

Since the update from grav-plugin-form 3.0.5, my ajax forms do not work as expected. I am not sure if this is caused by the plugin or by the way Grav manages languages.

This form worked as expected until the update:

title: 'Contact'
cache_enable: false
    action: /contact
    name: contact-form
    template: form-messages
    refresh_prevention: true

With this JS:

    url: form.attr('action'),
    type: form.attr('method'),
    data: form.serialize(),
    dataType: 'html',
    success: function() {},
    beforeSend: function() {},
    complete: function(result) {}

When the website has multiple languages, and paths are prefixed with the language code, this code no longer works since the update. There is an issue with redirection.

I put in place a temporary fix by hardcoding one language to the action path:

    action: /en/contact

It works, but it is not a good long-term solution: is this a bug of grav-plugin-form? Of Grav? Or is there a fundamentally better (and bug-free) way of submitting an ajax form in Grav?