LSC Cache is being cleared regularly - no idea how...

We took over a website for a client.
They have a number of plugins on there in WordPress, one of which is a plugin to udpate the Stock on products, via WP Import All Pro.

Our hosts are running a crawl and it caches the site. But then at regular internals something happens, products are cleared of cache, but other pages, including the homepage are cleared - thus turning a GTM score of C-A, down to F. With a "miss" on the caching check.

We are at a total loss as to the cause. I've run the site on a staging area, with that plugin disabled, and the speed is considerably better and holds it's cache.

Question is, how is it clearing the homepage cache?
I can give URLs etc if it helps.
I know that updating Woocomm Products clears the woocomm pages, but is it possible that is also clearing the homepage? And if so, is there a way to stop that?