Using a form from a different Wordpress subsite with NinjaForms

Question

I run a Wordpress multisite and want to display/use Ninjaforms from another subsite. For that I use the following code:

switch_to_blog(68);
Ninja_Forms()->display(10);
restore_current_blog();

This displays the form without a problem. But when I submit the form the placeholders in my configured email like {wp:post_title} or {post_meta:aktivitaet-datum_aktivitaet-datum-start} (from a custom field) do not work.

Did anyone else have this problem or is aware of a different solution how I may use forms from another subsite?