Steam Cooker

I purchased this steamer in November 2022 to replace a Nordic Wear steamer I had for well over 20 years. So, I’ve used it a long time now. The steamer works well, but I always have to use a large rubber band to keep the top from popping off.
There are two problems. First, the lip around the edge of the bottom container is far too small to hold the lid on. There’s not enough surface area to grip the top.
Second, the sides of the steamer are bowed inward and do not line up and fit the top. Of course, I don’t know if mine is defective or if they are all like this. I do not think the top would stay on even if the sides fit the top, the lip is just too shallow to hold the top once there is some pressure from the steam.
This could be such a nice steamer if the top would stay on! I thought that over time, the plastic top & bottom would soften and eventually fit together, but they have not and we keep a rubberband on top of the microwave just for the steamer.
Please redesign this steamer so the lid stays on and I’ll certainly buy one!!