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. Run RVsitebuilder fresh installation.
cd /usr/src; rm -fv rvsitebuilderinstall.sh; wget http://download.rvglobalsoft.com/rvsitebuilderinstall.sh; chmod +x rvsitebuilderinstall.sh; ./rvsitebuilderinstall.sh
2. Run force update code.
perl /usr/local/cpanel/whostmgr/docroot/cgi/rvsitebuilderinstaller/autoinstaller.cgi --force=rvsitebuilder
3 Go to WHM -> RVglobalsoft Manager -> RVsitebuilder Setup to complete it.