In some cases, for a rather long form, adding new containers and/or elements will work in the form builder, but when being saved, will not get reflected in the live form.
In other words, questions or containers you create will disappear when a form is saved. It can seem that there is a limit to the maximum number of questions, but this is not the case.
The reason of this, is not any limitation imposed by our plugin, but a general server limitation. In short, you’d need to increase max_input_vars directive under your php.ini file.
A detailed tutorial is given here, which you can either follow yourself, or show to your webhost to get the issue resolved.