Diving a little deeper, I see that the value berocket_product_brand_widget--1 is saved in the _transient_br_brands_cache_list 30k times, which is then causing clear_cache() in main.php:1456 to call delete_transient() over and over.
I’m not sure how the transient list was able to grow that large. I’ll leave that to the plugin developers.
For now I just deleted the _transient_br_brands_cache_list option from the db.
