Problem with Page Break

Glad you like the plugin, seiltanzer.

The way nextpage is implemented in most themes is responsible for this issue. If you are comfortable editing PHP code, then it’s fairly easy to fix. You just need to use add_filter with wp_link_pages so that you can give it a priority and place it above other plugins.

See this thread for a code snippet:
https://www.ads-software.com/support/topic/position-conflicts-nextpage-jetpack