Tomcat – causing Apache httpd (+mod_proxy_ajp) to drop connections

I have the following VirtualHost configured (Apache 2.2.22)

<VirtualHost *:80>
    ServerName ************

    ProxyRequests Off
    <Proxy *>
        Order deny,allow
        Allow from all
    </Proxy>

    ErrorLog /var/log/apache2/dalo-lt_error_log
    LogLevel warn
    TransferLog /var/log/apache2/dalo-lt_access_log

    ProxyPass / ajp://localhost:8009/
    ProxyPassReverse / ajp://localhost:8009/

    <Location />
        Order allow,deny
        Allow from all
    </Location>

</VirtualHost>

With the following in my Tomcat's server.xml (7.0.39)

<Connector port="8009" protocol="AJP/1.3"
           redirectPort="8443"
           connectionTimeout="60000"
           maxConnections="36864"
           maxThreads="600" />

<Connector port="8080" protocol="HTTP/1.1"
           connectionTimeout="20000"
           maxConnections="36864"
           maxThreads="600"
           redirectPort="8443" />

When I run my stress test through the vhost:80 + ajp, I start seeing dropped connections after a certain point. However, if i run the test directly through tomcat's http connector (:8080) I see no dropped connections whatsoever.

What is the best way to determine what is causing this?

Just for completeness, here are some settings from my apache2.conf

<IfModule mpm_prefork_module>
    StartServers          10
    MinSpareServers       10
    MaxSpareServers      20
    MaxClients          500
    MaxRequestsPerChild   0
</IfModule>

<IfModule mpm_worker_module>
    StartServers          4
    MinSpareThreads      50
    MaxSpareThreads      450
    ThreadLimit          256
    ThreadsPerChild      150
    MaxClients          300
    MaxRequestsPerChild   0
</IfModule>

<IfModule mpm_event_module>
    StartServers          4
    MinSpareThreads      50
    MaxSpareThreads      450
    ThreadLimit          256
    ThreadsPerChild      150
    MaxClients          300
    MaxRequestsPerChild   0
</IfModule>

Update:
Requesting server-status?auto yields the following while during the phase of the load test when requests are being dropped – so it looks to me like there are enough workers etc. to spare