You run force update RVsitebuilder on SSH and go to Setup in WHM -> RVglobalsoft Manager -> RVsitebuilder Setup. And it keeps opening error 500 in final stage.
The problem was on RVsitebuilder code not updated.
You can fix it by the following solution.
1. Enable ioncube in WHM > Tweak Setting > PHP > cPanel PHP loader check "ioncube" click Save.
cd /usr/src; rm -fv rvsitebuilderinstall.sh; wget http://download.rvglobalsoft.com/rvsitebuilderinstall.sh; chmod +x rvsitebuilderinstall.sh; ./rvsitebuilderinstall.sh
3. Run force update code.
perl /usr/local/cpanel/whostmgr/docroot/cgi/rvsitebuilderinstaller/autoinstaller.cgi --force=rvsitebuilder
4. Go to WHM -> RVglobalsoft Manager -> RVsitebuilder Setup to complete it.
If above doesn't help, please fix it by this guide : RVsitebuilder Manager error 500 after updated version