correct. for the time being you want to get a very vanilla installation of OBS up and running with at least a couple of scenes and media sources. but no plugins.
i recommend you start by completely removing streamelements and all associated files (from program files, program files (x86), and %appdata%) (make sure that you remove all plugins or 3rd party filters/addons you may be using. not just streamelements if applicable)
verify the problem still exists. if yes, continue. if not. you know what the problem is.
first create a new scene collection in OBS, create a couple of scenes add some sources. can you switch scenes as you would expect or does the problem persist? if it still is a problem there may be an issue with your installation of OBS and you may need to start over, make a backup of the %appdata%\obs-studio folder and, if you can, use the export option on the scene collection menu in OBS to export your main scene collection. then uninstall OBS. delete any remaining OBS folders from the %appdata% folder (not the backup you just made) and reinstall OBS. once this is complete repeat the same steps as before make a couple of scenes add some sources and verify. if all is working now, use the import tool and import your scenes from the backups. hopefully after this all will be working again and you can begin to add your plugins, but be sure to add them one at a time, restart and verify that everything still works each time.