Yes thanks this helped! I found out that wcvendors has its own action after saving and editing a product via their frontend form (wcv_save_product). So when this action is triggered, I’m running the Algolia sync_item (on that watch function).
With this change, I now see that it works when adding a new product to the index.
However, when I edit the product (e.g. from publish to draft), nothing happens (the index stays stale).
Any ideas? Is there anything different about indexing when a product is edited?