Yes a complete mess, but firstly what are you camera original files? I’m assuming BRAW as you said you reloaded them and they replaced the mp4 versions. So my next guess is that you started editing with mp4 proxies. Did they have the same name as the BRAW originals?
If you let Resolve create the proxy files from BRAW then you should have no issue relinking them to the BRAW camera originals on an external drive. If you are, then there was a problem creating the proxies and file names may have been changed. You may have to manually relink the BRAW to the proxies. If the name has been changed, I certainly hope the timecode wasn’t otherwise you are going to have to manually re-edit. Whatever you do, create a duplicate of your edit timeline so you can work in a copy in case you mess things up