Zend certified PHP/Magento developer

Products disappearing from Category pages – Tracking down the cause!

I have an unusual problem with a range of items on my Magento store that after a few days, disappear from the category pages. If I go into the back end, disable those specific items and then re-enable them again, once Magento re-indexes the products appear again (no manual re-index required, 5 minutes later it’s completed automatically by cron).
It’s very difficult to track down the cause! I have tried studying the database tables to identify the product ID’s which are effected (a range, 6-691 of over 3000 products) and comparing their data to products not effected, but cannot find the differences. I’ve also compared all the back end product data. Nothing seems to be amiss. I have been trying to hunt this down for a couple of weeks and have had to follow the procedure of disabling the products and re-enabling them 2 or 3 times, not an ideal solution. I also tried exporting all the products and re-importing and over-writing all the products concerned but no luck.

Has anyone experienced anything like this, and have you got any pointers on tracking down the cause? Are there any tools out there for Magento 2 which could possibly help identify problems like this by analysing the database?