After the babies arrived I bought some litter trays at Kmart to handle the load. The clips that lock the two halves together are part of the same moulded plastic as the top half, and eventually from clipping/unclipping, just wear through and break off. So I've ordered a fancier tray via Aliexpress to test out and if it locks better and is easy to clean I'll get some more. Sick of having these clips just break in my hand.