Out Of Stock Warning Disappeared From Shopping Cart

I'm currently in the process of setting up my shop (and getting to grips with Zen Cart). I made good inroads with my design, but I've just noticed that the "Out of Stock" warning no longer appears at the top of my shopping cart when I add more items than are currently available (the amount available of each item is set to show on each product page so I am sure that aspect is fine).

I don't need quantity buttons as most of my stock are handmade one-off's, but just to test what various aspects of the cart's page look like I added more than the available amount to my cart and just noticed I am no longer getting the warning text at the top of the page or *** against the items which have been over ordered. I've tried back-stepping some of the changes I made yesterday but am unable to pin point the problem.

I am using Zen Cart 1.3.8 and a few of my products have quantity attributes using stock_by_attributes_1-4-13 (which flung up another stock amount problem in the shopping cart, but that's another issue and didn't cause this error).

Can anyone tell me how to get the warning back? I've set my cart not to allow check-out if stocks are unavailable, but with no warning present a customer won't know why they are unable to check out.

I also have "Show available stock level in cart when less than order" set to true, but that's not working either.

Okay, it seems that only items with attributes will cause the stock level warning to work on the shopping cart, but then if other items are added into the cart it causes the same warning message to be added to them too (whether they are in stock or not).

Should I uninstall the attributes mod or is there a fix? How do I uninstall it?