Prevent TinyMce from rewritting simple urls

Hey all,

We recently upgraded our .Net solution to CMS 12 which seems to have changed the behaviour of our TinyMce editor and how it transforms internal links.

• sampleurl.html (the intended url)
• /EPiServer/CMS/Content/Shop/sampleurl,,72193/?epieditmode=false (what the url is transformed to, after upgrade)

Our Custom Config:

    internal static class CustomTinyMceConfig
    {
        public static IServiceCollection ConfigureTinyMce(this IServiceCollection services)
        {
            services.Configure<TinyMceConfiguration>(config =>
            {
                config.Default()
                    .AddPlugin("media wordcount anchor link code table")
                    .Toolbar("formatselect | epi-personalized-content anchor link numlist bullist indent outdent bold italic underline alignleft aligncenter alignright | image epi-image-editor media code | epi-dnd-processor | removeformat | fullscreen | table | row_props cell_props row_after row_before delete_row col_after col_before delete_col split_cells merge_cells")
                    .AddSetting("image_caption", true)
                    .AddSetting("image_advtab", true)
                    .InitializationScript("/ClientResources/js/tinymce/custom-init.js");
            });
            return services;
        }
    }

custom-init.js

define([], function () {
    return function (settings) {
        return Object.assign(settings, {
            /* 
             * call back to overwrite tinymce and epi urlconvert implementations for internal links
             * 
             * links defined in TinyMCE CMS blocks should take the form:
             *      href="{ PAGE_SIMPLE_URL }.html"
             *      
             * */
            urlconverter_callback: function (url, node, on_save) {
                var rval = url;
                // convert internal urls only
                if (url.includes('.html') && !url.includes('http')) {
                    rval = url.replace(/^.*[\\\/]/, '');;
                }
                return rval;
            }
        });
    };
});

Any ideas what could be causing this issue? Have tried quite a few things, including adding the "convert_url":false parameter to our custom config, which did not seem to work.

Thank you!