For users whose Controller is accessed through HTTPS with an Apache proxy, the following error is visible in the browser using developer tools:
<!DOCTYPE HTML PUBLIC "->
<html><head>
<title>404 Not Found</title>
</head><body>
<h1>Not Found</h1>
<p>The requested URL /controller/restui/userPreferenceManager/setGeneralUserPreference/SIMMachinesListController-stateId--SIM_MODE-4
.3-metricToggles
The following error message appears:

This issue is due to some versions of Apache unable to parse slashes in POST queries.
The error message does not affect any functionality, except for user preference retention between hard refreshes.
To resolve this issue, in the Apache config file (httpd.conf) turn on AllowEncodedSlashes NoDecode under <VirtualHost>.
Then restart the service.
Example:
AllowEncodedSlashes NoDecode
<Location /example/>
ProxyPass http://server:8080/example/ nocanon
</Location>
For more information, view this Stack Overflow solution for "Need to allow encoded slashes on Apache."