Sitemap update: crawl efficiency?

Hey everyone,

• Context: Following up on dynamic sitemaps and crawl budget. My app's dynamic sitemap seems to have developed a mind of its own.
• The Core Issue: It's just... not updating. New pages aren't showing up, old ones are lingering, and I'm pretty sure Google's bots are just shrugging.
• What I've Done So Far:
  • Checked the cron job – it's running like clockwork (or so it says).
  • Verified the sitemap generation script's permissions.
  • Manually triggered the script – it claims success, but the XML file remains stubborn.
  • Inspected server logs for any obvious failures (nothing screaming 'HELP ME!').
• The Weird Bit (Technical Snippet): When I try to force an update, the console output looks suspiciously normal, but the file just doesn't change. It's like my server is gaslighting me. Here’s a dummy output:

  [2024-07-23 10:00:01] INFO: Sitemap generator started.
  [2024-07-23 10:00:02] INFO: Fetched 1250 URLs from database.
  [2024-07-23 10:00:03] INFO: Writing sitemap.xml to /var/www/html/sitemap.xml
  [2024-07-23 10:00:03] INFO: Sitemap generation complete.
  

  This output looks fine, but the sitemap.xml file's last modified date and content remain unchanged.
• My Question: What could possibly be causing this stubborn refusal to update, even when the script reports success? Could it be caching at a level I'm not seeing, or something deeper impacting crawl efficiency and my overall crawl budget optimization efforts? Any ideas on how to debug this ghost in the machine would be amazing.
• Closing: Thanks in advance!