It seems Google isn't really deleting your reviews afterall.

Interesting article on Google reviews... I've noticed some chatter about Google 'deleting' reviews from business pages. After looking into it, it seems the reviews are still there, but the total count displayed is off. For example, I thought I lost 6 reviews, but after counting, I found they're all still visible. It seems like this might be a bug from an algorithm change that Google is currently addressing. https://www.seroundtable.com/google-local-reviews-decreasing-38873.html