Strange Behavior When Page Used as Front Page … /page/##### always works

Can you supply the address so that we can try to reproduce your issue?

Ah yes, so, going to http://intensewp.com/page/1 or http://intensewp.com/page/99999999999 ends up on the same “This is the front page” as does simply going to http://intensewp.com/. But, interestingly, going to http://intensewp.com/page/ or http://intensewp.com/page/abc generates an “Oops! That page can’t be found.” error message on the page.

Note that I was using Mac Firefox 38.0.5 with a cleared cache.

Just to be sure, ALL plugins are disabled and the your using an unmodified Twenty Fifteen theme, right?

Just reproduced your issue using Mac Firefox 38.0.5 and a new install of WordPress 4.2.2 (with no active plugins and an unmodified Twenty Fifteen 1.2) running on MAMP 3.3.

Setup:
– MAMP 3.3
– WordPress 4.2.2
– Permalink Settings > Common Settings > Day and name (default)
– Created page titled The Front Page
– Settings > Reading > Front page displays > The Front Page

Going to http://localhost/wordpress/ took me to http://localhost/wordpress/
–> expected behavior.
Going to http://localhost/wordpress/page/1 took me back to http://localhost/wordpress/
–> different than what was seen on your site.
Going to http://localhost/wordpress/page/2 kept me on http://localhost/wordpress/page/2
–> same as seen on your site. not sure whether this is expected behavior.
Going to http://localhost/wordpress/page/99999999999 kept me on http://localhost/wordpress/page/99999999999
–> same as seen on your site. not sure whether this is expected behavior.
Going to http://localhost/wordpress/page/ gave error “Oops! That page can’t be found.”
–> same as seen on your site. guessing this is expected behavior.
Going to http://localhost/wordpress/page/abc gave error “Oops! That page can’t be found.”
–> same as seen on your site. guessing this is expected behavior.

So, for me, the question of the day is what is expected behavior when someone goes to /page/2, /page/99999999999, etcetera?