WP Super Cache stops working after a few hours

Hi everyone,

We migrated a WordPress website from a Linux dedicated VM (hosting both web server and mysql) to Azure App Services (Windows platform / PHP 7.4 / 64 bit) + Azure MySQL. Of course we had to change some paths in the database (like /var/wwwroot to C:\home\site\wwwroot), we did it with the help of Search-and-ReplaceDB.

The site uses WP Super Cache since the beginning. When the webapp is freshly started, everything runs fine and the plugin is doing its job: cache files are generated at first access then served until expiration. Ok.

But after a random few hours, the cache files are removed (which is the normal behaviour when they expire) but are not generated anymore.

Debug log when it works:

10:00:18 5700 /litisafe/ wpsc_get_auth_cookies: no auth cookies detected
10:00:18 5700 /litisafe/ wpsc_is_caching_user_disabled: false
10:00:18 5700 /litisafe/ wp_cache_get_cookies_values: return:
10:00:18 5700 /litisafe/ supercache dir: ABSPATH/wp-content/cache/supercache/www.degaullefleurance.com/litisafe/
10:00:18 5700 /litisafe/ wp_cache_get_cookies_values: return:
10:00:18 5700 /litisafe/ Fetched gzip static page data from supercache file using PHP. File: ABSPATH/wp-content/cache/supercache/www.degaullefleurance.com/litisafe/index-https.html.gz
10:00:18 5700 /litisafe/ wp_cache_serve_cache_file: checking age of cached vs served files.
10:00:18 5700 /litisafe/ wp_cache_serve_cache_file: Send 304 Not Modified header.

Debug log when it does not work:

09:30:12 5320 /litisafe/ wpsc_get_auth_cookies: no auth cookies detected
09:30:12 5320 /litisafe/ wpsc_is_caching_user_disabled: false
09:30:12 5320 /litisafe/ wp_cache_get_cookies_values: return:
09:30:12 5320 /litisafe/ supercache dir: C:\home\site\wwwroot\wp-content/cache/supercache/www.degaullefleurance.com/litisafe/
09:30:12 5320 /litisafe/ No Super Cache file found for current URL: C:\home\site\wwwroot\wp-content/cache/supercache/www.degaullefleurance.com/litisafe/index-https.html
09:30:12 5320 /litisafe/ wp_cache_get_cookies_values: return:
09:30:12 5320 /litisafe/ In WP Cache Phase 2
09:30:12 5320 /litisafe/ Setting up WordPress actions
09:30:12 5320 /litisafe/ Created output buffer
09:30:12 5320 /litisafe/ wp_cache_get_cookies_values: return:
09:30:12 5320 /litisafe/ wpcache_do_rebuild: doing rebuild for C:\home\site\wwwroot\wp-content/cache/supercache/www.degaullefleurance.com/litisafe/
09:30:12 5320 /litisafe/ wpcache_do_rebuild: exiting as directory is not a directory: C:\home\site\wwwroot\wp-content/cache/supercache/www.degaullefleurance.com/litisafe/
09:30:17 5320 /litisafe/ wpsc_is_caching_user_disabled: false
09:30:17 5320 /litisafe/ Output buffer callback
09:30:17 5320 /litisafe/ wp_cache_get_cookies_values: return:
09:30:17 5320 /litisafe/ Anonymous user detected. Only creating Supercache file.
09:30:17 5320 /litisafe/ wpsc_is_caching_user_disabled: false
09:30:17 5320 /litisafe/ wpsc_get_realpath: directory does not exist - C:\home\site\wwwroot\wp-content/cache/supercache/www.degaullefleurance.com/litisafe/
09:30:17 5320 /litisafe/ wp_cache_get_ob: not caching as directory does not exist.
09:30:17 5320 /litisafe/ wp_cache_shutdown_callback: collecting meta data.
09:30:17 5320 /litisafe/ Did not write meta file: meta-wp-cache-0530eadb18e544567b9a28d5771b389b.php

It does not seem to be a permissions problem since the plugin is allowed to create folders and files when freshly started (and other plugins like matomo write in the same /cache folder with success).

How could we dig further in the logs to understand where does the problem come from ?

Any help warmly appreciated ??