Usermin redirects causing "Corrupted Content Error"

First of all i'm not sure why my issue was closed on Authentic theme github. Doesnt matter if i'm the only one reporting this issue, its still a issue not caused by any of my actions. So i'm opening this here.

• CentOS Linux 7.4.1708 / Webmin 1.870 / Virtualmin 6.02 / Usermin 1.720
• Win7 / FF / 57.0.2 (64-bit)

Case 1 (working ok):
Authentic theme settings - Default pages:
Default tab after logging in to Webmin - Webmin
Default module for Webmin - empty
Default page for Virtualmin - empty
Default tab after logging in to Usermin - Usermin

After successful login i'm prompted with Usermin (def. tab Usermin).

Case 2 (bugged):
Authentic theme settings - Default pages:
Default tab after logging in to Webmin - Webmin
Default module for Webmin - empty
Default page for Virtualmin - empty
Default tab after logging in to Usermin - Mail

After successful login i'm prompted with:

Corrupted Content Error
The site at https://mydomain.com:XXXXX/ has experienced a network protocol violation that cannot be repaired.
The page you are trying to view cannot be shown because an error in the data transmission was detected.
Please contact the website owners to inform them of this problem.

This is what i have in Usermin logs:

Reloading the page will remove this error and open Usermin but the default tab didnt change and Usermin tab will be first to show up. If i move back "Default tab after logging in to Usermin" to "Usermin" the problem is gone.

Additional info:
Error "Corrupted Content Error" is caused in FF when there are some conflicts with HTTP redirects. Tested this with Opera and no error so obviously FF have more strict rules. Plus when i used Opera i was able to login without any problem but the default tab was Usermin and not Mail. So something with redirects doesnt work when switched to "Mail" tab as default.
Changed the theme for everything to "Virtualmin Framed theme", in Usermin settings set "Read mail" as default option and tested with Opera and FF. Both logins worked fine and i was redirected to the right module. So definitely something is broken with my Authentic theme and must be during the updates. Two things that i every changed with Authentic theme was turning off hotkeys and changing "Default tab after logging in to Usermin". The rest was left untouched from the day when the theme was first introduced (my initial install was way before Authentic came out).

So i would like to correct Joe when he stated "I'm guessing that means Usermin was killed by the OOM killer in the middle of the request". This server never hit OOM or had any other problems. For now all evidence is pointing to some problems with Authentic theme. Again it must be during the update because i didnt change anything or made any action what could be the reason for this issue to appear. The log files (all of them not just Usermin) doesnt show any trace of what is going on. I tested many times to see if some other problem will show up but nothing. Something must be wrong in a way Authentic theme is handling redirects and (maybe) Usermin not able to properly follow such instructions.

Keep in mind this Virtualmin installation is 3 years old, so all major changes (e.g. Vmin 6.0, Authentic, etc...) came long after this system was build.