Php 5.5.36? Redirects To Url-Encoded Paths?

So on a server running php 5.5.36 I am continually running into an issue where things like store import or site upgrades just redirect to blank pages. I have no errors in error_log, apache or anywhere else I can think to look. If I set dev mode, I still just get a blank page.

Is there some weird flag I'm not flipping or something?

Example output:

{click upgrade, validate store path or whatever}
200 OK, no data

right this is on a 4.3.6 install and also trying to upgrade from 4.2.2 - > whatever is next

Path got link-a-fied. This is what I'm seeing

If I'm not mistaken, 4.3.6 requires a minimum PHP version of 5.6.

Be sure to change any error_reporting() functions you see are set to error_reporting(E_ALL) and do not remove any NOTICES or DEPRECATED errors.