Are `lastmod` Timestamps in Dynamic Sitemaps Inaccurate Due to Aggressive Sitemap Caching?

Following up on my previous thread about Googlebot's intermittent indexing issues with our dynamic sitemap, I'm now wondering if our aggressive server-side sitemap caching is causing the lastmod timestamps to be inaccurate, potentially confusing Googlebot and affecting our crawl efficiency. Are there specific strategies or configurations to ensure lastmod accuracy when using aggressive caching for dynamically generated sitemaps? Anyone faced this before?