It seems that you are facing an issue with duplicate images appearing on email templates in Magento 2.4.3-p1. You have already tried applying a patch and using CSS, but the problem persists. I'll try to help you with some additional steps you can take to address this issue.
Clear cache and reindex: Make sure to clear the cache and reindex your Magento installation after applying any changes or patches. This can be done through the command line or via the Magento admin panel.
Verify the block and template code: Double-check the code for the custom block and email template to ensure there are no errors or inconsistencies. Verify that the block ID you are using in the email template corresponds to the correct block.
Check for conflicting customizations or extensions: If you have made any customizations or have installed third-party extensions, there could be conflicts causing the duplicate image issue. Try disabling any customizations or extensions related to email templates or blocks and see if the problem persists. If the issue is resolved, you may need to investigate further to identify the conflicting customization or extension.
Test with a default email template: Create a new email template using only default Magento blocks and test if the duplicate image issue still occurs. This will help determine if the problem is specific to your custom block or if it is a more general issue with email templates.
Debug and log: Enable logging and debugging in your Magento installation to gather more information about the issue. Check the system logs and error logs for any relevant messages that could provide insights into the problem.
Reach out to Magento support or community: If you have exhausted all troubleshooting steps and the issue persists, it may be beneficial to seek assistance from the Magento community or Magento support. Provide them with detailed information about the steps you have taken and any relevant error messages or logs.
Remember to always back up your Magento installation before making any changes or applying patches to avoid any potential data loss or further issues.