Issues like this after an upgrade can often stem from changes in the underlying codebase, configuration, or caching mechanisms. Since you're encountering the issue specifically in Drupal 10.1.0 and it's related to cache, here are a few steps you can take to investigate and potentially resolve the problem:
Check for Updates and Known Issues:
First, make sure you're using the latest version of your custom modules and themes, as well as any contributed modules. Also, check the release notes and issue queues of these modules to see if there are known issues related to caching and rendering in Drupal 10.1.0.
Review Your Custom Code:
If you have custom code in your application, review it to ensure it's compatible with Drupal 10.1.0. Pay special attention to any areas related to rendering, caching, or block visibility.
Debugging and Logging:
Enable debugging and check for any error messages or logs that might point to the issue. Drupal's watchdog logs (/admin/reports/dblog) can be helpful in diagnosing problems.
Check Render and Cache Contexts:
If you're using custom blocks or templates, make sure that you're using the correct render and cache contexts. Cache contexts determine when a cached version of a block is reused. Incorrect or missing cache contexts can lead to unexpected behavior, especially when dynamic content is involved.
Flush Caches After Upgrade:
It's common to experience cache-related issues after upgrading. After upgrading to Drupal 10.1.0, it's a good practice to flush all caches (using Drush or the Drupal admin interface) to ensure that the caches are rebuilt and potentially fix any caching-related inconsistencies.
Dynamic Page Cache and Block Cache:
Since disabling the "dynamic page cache" resolves the issue, this might indicate that there's a conflict between your custom rendering and the dynamic page caching. Make sure that your custom rendering logic is compatible with dynamic page caching. You might need to use cache context or vary the cache based on conditions.
Check Block Visibility Configuration:
Verify that the block visibility configuration (based on content type, path, role, etc.) is correctly set up for the blocks that are causing issues. Incorrect visibility settings might cause blocks not to display under certain circumstances.
Module Compatibility:
Some contributed modules might not be fully compatible with the latest Drupal version. If any of your contributed modules are critical for your application, ensure that they are updated to versions compatible with Drupal 10.1.0.
Regression Testing:
If the issue persists, consider performing regression testing by reverting to Drupal 10.0.10 and seeing if the issue is resolved. This could help confirm whether the problem is specific to Drupal 10.1.0.
File a Bug Report:
If you're unable to resolve the issue after investigating the above steps, consider filing a bug report in the Drupal issue queue. Provide as much detail as possible about your setup, the issue, and any steps to reproduce it.
Remember that diagnosing and resolving issues like this might require a combination of debugging, code review, and experimentation. It's a good practice to work in a staging environment or have backups available while troubleshooting.
