I have a feeling it has to do with wordpress?
It probably is, and I'm sure there's some internal to wordpress way of handling it using their rewrite API and (probably) the post_rewrite_rules hook. (More info at the wordpress stack exchange.
But if that doesn't work, you can always try the P
flag to internally proxy the request so that the REQUEST_URI
that wordpress' controller sees is the one without all the stuff after the /page/
(which is most likely what is causing wordpress to puke).
RewriteRule ^community-alumni/conference-services/page/(.*)$ /community-alumni/conference-services/?pagetab=$1 [L,P]