Below is a tight, practical map for WordPress (and the general pattern behind it) so you can eliminate these clashes and encode your standard once.

1) What’s actually colliding (WordPress reality)

When you use /%postname%/, every top-level thing competes for the same path:

• Pages (wp_posts.post_type='page')
• Posts (post)
• Custom Post Types (CPTs)
• Terms (category/tag archives)
• Attachments
• Endpoints (/feed/, /page/2/, etc.)
• Legacy redirects (.htaccess, plugins, CDN) and caches

By default, WordPress resolves by rewrite rule order (pages and attachments tend to win) and whatever extra rules a plugin stuffed into .htaccess. So:

• A page /cable-internet and a post /cable-internet → page wins.
• A term cable-internet + page cable-internet → behavior depends on rewrite precedence and bases (e.g., /category/), but can still collide if bases were removed.
• A page /cable-internet-overview + post changed from /cable-internet-overview → stale redirects, caches, or identical slugs in different post types cause “flip-flopping.”

2) One-time structural fix (Language-first routing contract)

Decide a grammar for your site and enforce it. The simplest, robust pattern:

• Pages: /services/... or /site/... (choose one clear namespace)
• Posts (blog): /blog/%postname%/
• Docs/Guides (if CPT): /docs/%postname%/
• Categories/Tags: keep the base (/category/, /tag/) or use distinct ones (/topics/, /labels/)
• Attachments: disable public attachment pages or put them under /media/

This single decision removes 95% of collisions because post types no longer share the root. It’s language standardization applied to routing.

Concretely:

1. Settings → Permalinks → set Custom Structure for posts:
   /blog/%postname%/
2. For CPTs, set rewrite => [ 'slug' => 'docs', 'with_front' => false ].
3. Keep category/tag bases distinct (don’t strip them to root).
4. Disable attachment pages (redirect to parent) or namespace them.

3) Immediate cleanup steps on your site

1. Flush rewrites: Settings → Permalinks → Save (even if unchanged).
2. .htaccess sanity: ensure a single WordPress block; move plugin/handwritten rules above or below intentionally—don’t interleave inside the WP block.
3. Purge caches: page cache, CDN, browser cache; stale caches masquerade as “random” routing.
4. Clear redirect plugins: remove old redirects that now point two ways.
5. Nail canonical: use a SEO plugin to emit rel=canonical for each competing path while migrating.

4) Find conflicts fast (queries & checks)

A) duplicate slugs across post types

SELECT post_name, COUNT(*) c
FROM wp_posts
WHERE post_status IN ('publish','private')
  AND post_type IN ('page','post','attachment','your_cpt')
GROUP BY post_name
HAVING c > 1
ORDER BY c DESC, post_name;

B) posts/pages sharing slugs with terms

SELECT p.post_name
FROM wp_posts p
JOIN wp_terms t ON t.slug = p.post_name
JOIN wp_term_taxonomy tt ON tt.term_id = t.term_id
WHERE p.post_status IN ('publish','private')
  AND p.post_type IN ('page','post','your_cpt');

C) reserved endpoints posing as content

Watch for slugs like feed, page, comments, year/month numbers, author, search, embed. Don’t use them as content slugs.

5) Enforce the grammar (so the conflict can’t recur)

A) Prefix posts (and/or CPTs)

• Posts: set /blog/%postname%/ and keep it forever.
• CPTs: when you register_post_type, always give each a unique rewrite['slug'].

B) Guardrails in code (reject conflicting slugs)

Drop a filter to auto-rename a new post/page if it collides with an existing route:

add_filter('wp_insert_post_data', function($data, $postarr) {
  if (in_array($data['post_status'], ['auto-draft','trash'])) return $data;

  $slug = $data['post_name'];
  // Block reserved and known-conflict slugs:
  $reserved = ['feed','page','comments','author','search','embed'];
  if (in_array($slug, $reserved)) $data['post_name'] .= '-content';

  // Enforce namespace for posts (if someone tries to bypass UI):
  if ($data['post_type'] === 'post') {
    // nothing to change in slug; routing is already /blog/%postname%/
  }

  return $data;
}, 10, 2);

C) Disable attachment pages

add_action('template_redirect', function() {
  if (is_attachment()) {
    if ($parent = get_post()->post_parent) {
      wp_redirect(get_permalink($parent), 301);
      exit;
    }
    wp_redirect(home_url('/'), 301);
    exit;
  }
});

6) Migration without breakage (when you change structure)

• Generate 301s from old → new with a redirects plugin or server rules.
• Keep redirects flat and minimal; avoid chains.
• Reindex sitemaps; submit in Search Console; purge CDN.

7) If you must keep /%postname%/ (no prefixes)

Then you need strict uniqueness at the root:

• Never create a page and a post with the same slug.
• Never strip category/tag bases.
• Block “danger slugs” (above list).
• Use a pre-publish checker to scan for existing post_name AND matching term slugs.
• Expect occasional surprises from plugins adding rewrite endpoints.

8) The deeper principle (your thesis)

Routing is a language contract. When the grammar is ambiguous, the server “interprets” and picks a meaning. When the grammar is namespaced and canonical, interpretation disappears; conflict becomes impossible. Code starts communicating properly because the language of addresses is coherent.

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If you want, give me:

1. Your current permalink structure,
2. Any CPTs (and their desired bases),
3. A short list of example slugs (like cable-internet, cable-internet-overview),

…and I’ll return:

• a proposed routing grammar (pages/posts/CPTs/terms),
• the exact .htaccess (or Nginx) adjustments,
• a one-shot SQL + WP-CLI checklist to fix and enforce it,
• and 301 mappings so everything keeps ranking while we standardize the speech.