subsites appears to redirect to itself

I have a multisite network using subdirectories like this:

example.com
example.com/issue001
example.com/issue002
…
example.com/issueNNN

My parent site returns 200. All good.

My subsites look OK in a browser, but when analysing using an SEO analyser tool, it reports them as returning 301 and having no title/meta/first para/body etc, and using google webtools “fetch as googlebot” I get this:

example.com/issue001:
The page seems to redirect to itself. This may result in an infinite redirect loop. Please check the Help Center article about redirects.

HTTP/1.1 301 Moved Permanently
Date: Mon, 10 Sep 2012 10:45:39 GMT
Server: Apache/1.3.42 (Unix) Sun-ONE-ASP/4.0.2 Resin/2.1.13 mod_fastcgi/2.4.6 mod_log_bytes/1.2 mod_bwlimited/1.4 mod_auth_passthrough/1.8 FrontPage/5.0.2.2635 mod_ssl/2.8.31 OpenSSL/0.9.8e-fips-rhel5
X-Pingback: https://example.com/issue001/xmlrpc.php
X-Powered-By: PHP/5.3.15
Location: https://example.com/issue001/
Keep-Alive: timeout=15, max=100
Connection: Keep-Alive
Transfer-Encoding: chunked
Content-Type: text/html; charset=UTF-8

Could this be a problem with the “www” redirect to “non-www” and multisite interfering with each other?

Here is my .htaccess file contents

RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]

# uploaded files
RewriteRule ^([_0-9a-zA-Z-]+/)?files/(.+) wp-includes/ms-files.php?file=$2 [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule  ^[_0-9a-zA-Z-]+/(wp-(content|admin|includes).*) $1 [L]
RewriteRule  ^[_0-9a-zA-Z-]+/(.*\.php)$ $1 [L]
RewriteRule . index.php [L]
<Files 403.shtml>
order allow,deny
allow from all
</Files>