Adding products from a shared cart seems to be working intermittently

Hello, I installed the plugin on a client’s store and it seems to be working only intermittently.

I added a product to the cart, then proceeded to share it via a link. After that I opened up a different browser (so I could use the store as a non-logged in user) and navigated to the shared link. The page appeared just fine and then I clicked the “Buy all” button.

Thing is, it seems to add the shared products to the cart only some times and not every time. Most of the time after clicking the Buy all button it redirects to the cart page and it says “No products in cart”. Sometimes it work correctly, though, after some page refreshes. I couldn’t find a pattern, though.

I am using Openlitespeed with the LsCache plugin, object caching via Memcached, and the Woodmart theme. I tried disabling the LsCache plugin but it didn’t seem to help. In any case the cart and checkout pages are already non-cacheable as per configuration.

Is there anything else I can check? It really works only sometimes but not every time.