Grails Spring Security appending :8080 to URL when behind Apache proxy

Grails Spring Security appending :8080 to URL when behind Apache proxy

In production my Grails app is running on Tomcat port 8080 and sits behind
an Apache proxy; port 80. All functions work except for authentication.
When a user tries logging into the app Spring Security appends :8080 to
the target URL and the connection times out since the request can't be
routed.
I have already set the following in config.groovy but no success:
grails.serverURL = "http://domain.tld/${appName}"
grails.plugins.springsecurity.portMapper.httpPort = "80"
grails.plugins.springsecurity.portMapper.httpsPort = "443"
The issue occurs when I try with either built-in authentication or OpenID.
The app had been working well for over 6 months before my hosting provider
made changes by plugged a hole and started blocking port 8080 from the
outside.
I just need Spring Security to write the URL without :8080
Any help is appreciated, thanks!