TL;DR: Changing my characters password seemed to have solved the problem.

So I had problems with the "Downloading data..." screen when zoning to Sauromague and West Sarutabaruta today.
Needing to go through those zones, I uninstalled and reinstalled and then installed again on top of that installation, tried the Ashita.zip and rebooted and what not.
The problem seemed to be "spreading" at some point as I got the bug for the moghouse in port jeuno too.
I had to do a lot of session clearing and unstuck a lot of times while I was attempting to find a solution (wasn't trying to exploit or such... I know it probably looks odd in the logs, with all those actions taken).

Not sure why I decided to change my password but I faintly recalled something related to another problem while searching the forum.

-- Another possible reason, which seems doubtful; is the quest "Riding on the Clouds". I managed to work around the areas I couldn't get into to finish this one up and I did clear it with Maat. Only after that did I try to enter Sauromague again and was successful.

Hope it'll help others if they stumble on this problem at some point!
Cheers!