Cache being regenerated every time on some pages

Most pages on my site cache perfectly but there are a range of pages that never cache. A supercache file is built for the page but it regenerates a new one every time the page is requested. The debug gives me no clues. It just keeps saying “No wp-cache file exists” but it does, I can see it on the file system.

07:04:07 /project-galleries/residential-by-type/interiors/ supercache dir: /home/dsarchitecture/public_html/wp-content/cache/supercache/new.dsarchitecture.com.au/project-galleries/residential-by-type/interiors/
07:04:07 /project-galleries/residential-by-type/interiors/ No wp-cache file exists. Must generate a new one.
07:04:07 /project-galleries/residential-by-type/interiors/ In WP Cache Phase 2
07:04:07 /project-galleries/residential-by-type/interiors/ Setting up WordPress actions
07:04:07 /project-galleries/residential-by-type/interiors/ Created output buffer
07:04:07 /project-galleries/residential-by-type/interiors/ scheduled wp_cache_gc for 10 seconds time.
07:04:13 /project-galleries/residential-by-type/interiors/ Output buffer callback
07:04:13 /project-galleries/residential-by-type/interiors/ Anonymous user detected. Only creating Supercache file.
07:04:13 /project-galleries/residential-by-type/interiors/ Gzipping buffer.
07:04:13 /project-galleries/residential-by-type/interiors/ Writing non-gzipped buffer to supercache file.
07:04:13 /project-galleries/residential-by-type/interiors/ Writing gzipped buffer to supercache file.
07:04:13 /project-galleries/residential-by-type/interiors/ Renamed temp supercache file to /home/dsarchitecture/public_html/wp-content/cache/supercache/new.dsarchitecture.com.au/project-galleries/residential-by-type/interiors/index.html
07:04:13 /project-galleries/residential-by-type/interiors/ Renamed temp supercache gz file to /home/dsarchitecture/public_html/wp-content/cache/supercache/new.dsarchitecture.com.au/project-galleries/residential-by-type/interiors/index.html.gz
07:04:13 /project-galleries/residential-by-type/interiors/ Writing gzip content headers. Sending buffer to browser
07:04:13 /project-galleries/residential-by-type/interiors/ wp_cache_shutdown_callback: collecting meta data.
07:04:31 /project-galleries/residential-by-type/interiors/ supercache dir: /home/dsarchitecture/public_html/wp-content/cache/supercache/new.dsarchitecture.com.au/project-galleries/residential-by-type/interiors/
07:04:31 /project-galleries/residential-by-type/interiors/ No wp-cache file exists. Must generate a new one.
07:04:31 /project-galleries/residential-by-type/interiors/ In WP Cache Phase 2
07:04:31 /project-galleries/residential-by-type/interiors/ Setting up WordPress actions
07:04:31 /project-galleries/residential-by-type/interiors/ Created output buffer
07:04:39 /project-galleries/residential-by-type/interiors/ Output buffer callback
07:04:39 /project-galleries/residential-by-type/interiors/ Anonymous user detected. Only creating Supercache file.
07:04:39 /project-galleries/residential-by-type/interiors/ Gzipping buffer.
07:04:39 /project-galleries/residential-by-type/interiors/ Writing non-gzipped buffer to supercache file.
07:04:39 /project-galleries/residential-by-type/interiors/ Writing gzipped buffer to supercache file.
07:04:39 /project-galleries/residential-by-type/interiors/ Renamed temp supercache file to /home/dsarchitecture/public_html/wp-content/cache/supercache/new.dsarchitecture.com.au/project-galleries/residential-by-type/interiors/index.html
07:04:39 /project-galleries/residential-by-type/interiors/ Renamed temp supercache gz file to /home/dsarchitecture/public_html/wp-content/cache/supercache/new.dsarchitecture.com.au/project-galleries/residential-by-type/interiors/index.html.gz
07:04:39 /project-galleries/residential-by-type/interiors/ Writing gzip content headers. Sending buffer to browser
07:04:39 /project-galleries/residential-by-type/interiors/ wp_cache_shutdown_callback: collecting meta data.
07:04:43 /project-galleries/residential-by-type/interiors/ supercache dir: /home/dsarchitecture/public_html/wp-content/cache/supercache/new.dsarchitecture.com.au/project-galleries/residential-by-type/interiors/
07:04:43 /project-galleries/residential-by-type/interiors/ No wp-cache file exists. Must generate a new one.
07:04:43 /project-galleries/residential-by-type/interiors/ In WP Cache Phase 2
07:04:43 /project-galleries/residential-by-type/interiors/ Setting up WordPress actions
07:04:43 /project-galleries/residential-by-type/interiors/ Created output buffer
07:04:50 /project-galleries/residential-by-type/interiors/ Output buffer callback
07:04:50 /project-galleries/residential-by-type/interiors/ Anonymous user detected. Only creating Supercache file.
07:04:50 /project-galleries/residential-by-type/interiors/ Gzipping buffer.
07:04:50 /project-galleries/residential-by-type/interiors/ Writing non-gzipped buffer to supercache file.
07:04:50 /project-galleries/residential-by-type/interiors/ Writing gzipped buffer to supercache file.
07:04:50 /project-galleries/residential-by-type/interiors/ Renamed temp supercache file to /home/dsarchitecture/public_html/wp-content/cache/supercache/new.dsarchitecture.com.au/project-galleries/residential-by-type/interiors/index.html
07:04:50 /project-galleries/residential-by-type/interiors/ Renamed temp supercache gz file to /home/dsarchitecture/public_html/wp-content/cache/supercache/new.dsarchitecture.com.au/project-galleries/residential-by-type/interiors/index.html.gz
07:04:50 /project-galleries/residential-by-type/interiors/ Writing gzip content headers. Sending buffer to browser
07:04:50 /project-galleries/residential-by-type/interiors/ wp_cache_shutdown_callback: collecting meta data.