I'm getting a "Not Found" error message on the Cart page that I cannot figure out. It doesn't happen for every user, but it happens consistently for the users that see it. It's also accompanied occasionally by an Internal Error message that replaces the Cart after it has loaded. Trying to track this down, I've disabled all extensions and switched back to the Base Theme. Also turned off Scriptable Cart. I've reviewed the XHR requests and searched the Script Execution Log repeatedly. Working from version 2019.1, in a Sandbox account. Any ideas what could be causing this?

Look at the network tab

I must have looked there 100 times and missed it... but it is coming from the ProductList.Service.ss file... So, related to the wishlists somehow?

what's the exact service output? that is weird!

So... this morning I dug into it and traced it back to a bad Configuration of the Wishlist templates. It wasn't able to load the later template and that caused the error. I ended up fixing it by overwriting the whole Configuration with a copy from an unmodified domain. A little tedious to redo all the configuration settings, but not too bad. Thanks again for your help Pablo!

Thanks to you for sharing the fix! 🙂