“Invalid Template File” CRIT once a day for system built in templates . Do I worry or ignore it?

Every day at the same time I get a whole ream of CRIT alerts for invalid template files

[2024-01-25T02:40:23.971560+00:00] main.CRITICAL: Invalid template file: 'widget/static_block/default.phtml' in module: 'Magento_Cms' block's name: 'widgetblock_4' 
[2024-01-25T02:40:23.971774+00:00] main.CRITICAL: Invalid template file: 'widget/link/link_block.phtml' in module: 'Magento_Cms' block's name: 'widgetpagelink_6' 
[2024-01-25T02:40:24.079384+00:00] main.CRITICAL: Invalid template file: 'widget/static_block/default.phtml' in module: 'Magento_Cms' block's name: 'widgetblock_5' 
[2024-01-25T02:40:24.095451+00:00] main.CRITICAL: Invalid template file: 'widget/static_block/default.phtml' in module: 'Magento_Cms' block's name: 'widgetblock_6'

Having changed the time of all my cron jobs to isolate, it seems to happen after catalogrule_apply_all – this ends with invalidating the price index which triggers cache cleaning.

These template files are there and valid, the errors happen once and not again so I want to ignore it but it bugs me to understand why it happens. CRIT to me means “needs attention” surely?

Is it about the cached block that has vanished rather than the template?

This is on 2.4.6-p3