Ok have solved it by going through the docs again and using page decorators. The docs kinda make it sound like these are optional but my guess they are a requirement for multiple pagination on the same page.
from endless_pagination.decorators import page_template
@page_template('entry_index_page.html')
@page_template('by_percentage_saved.html', key='by_percentage_saved')
def entry_index(request, parent_cat, child_cat, template='entry_index.html',
extra_context=None):