V2.4.3-p1 indexing breaks intermittantly

[GreyWolfSystems]

We just upgraded to v2.4.3-p1 and have it installed in a subdirectory.  We have ALL cron jobs shutoff.

Every so often, the site loses the indexing and is broken.  The easy fix is to run bin/magento index:reindex and the site runs perfectly.

Any idea what would cause the indexes to be broken if cron is completely disabled?

[Sanjay Jethva]

@GreyWolfSystems 

There are two ways to run indexing automatically in Magento:
1. Update by schedule (cron base)
2. Update on save (when product/category save/update in admin)

If you aren't able to re-index cron base then you can set indexing mode using "Update on save" from:
Admin -> System -> Index Management