What version are you running?
2.5.7
What's the URL of the page containing the problem?
Any page of the FIRST created site
What steps will reproduce the problem?

create a first site (named "/rb1/") with rb-site
create a second site (named "/rb2/") on the same host with rb-site (using a different root-doc)
try to load the homepage of the first site


What is the expected output? What do you see instead?
Both sites should be available, i get HTTP 404 on the FIRST site created.
What operating system are you using? What browser?
Linux Ubuntu 16.04 LTS / Firefox 50
Please provide any additional information below.
As fas as i understand, the Django configuration of both sites use the same alias (os.environ['DJANGO_SETTINGS_MODULE'] = "reviewboard.settings"). Other aliases are site specific (rb1 vs rb2).