Symptoms
When you customer tries to click any link that has branding at Control Panel, It will automatically use HTTPS instead of http even though the link do not have any https installed.
Cause
HTTP Strict Transport Security was enabled in branding_htaccess.
Resolution
Access the branding server and comment out the following line :
# grep Strict-Transport-Security /usr/local/pem/vhosts/100001/webspace/httpsdocs/uibrand/.branding_htaccess
header always set Strict-Transport-Security "max-age=31536000; includeSubDomains"