A user made a script fix via TamperMonkey to the muti tag issue here is the script
// ==UserScript==
// @name Rule34 URL Fixer
// @version 1
// @grant none
// @include https://rule34hentai.net/*
// ==/UserScript==

window.addEventListener('load', function() {
var currentURL = window.location.href;
var fixedURL = currentURL.replace(/%20|\s/g, '+');
if (currentURL !== fixedURL) {
window.location.href = fixedURL;
}
}, false);

Add that via Installed Userscripts and it will redirect you when you search for multiple tags.
Use this until a solution is found for this very troublesome bug.

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Revision 1 by Rastafarian at 2024-04-12 05:19:18