I've not had any issues with the lid coming off. Has it done that since new, maybe it's a defect. I've been impressed with the amount of abuse, water and even pressuring washing the box will take without leaking. I was a little concerned about the pressure washing, but happily had no issues. It does have a drain plug but I've never had to use it.I have the Yamaha box. For the most part I like it. I don't like that the lid shoots off if you fart to hard while riding.
I am going to cut some rubber spacers and see if I can tighten it up a bit more. Other than that I really like it and I think it will be an easy fix.
better late than never. Here's some pics of my yamaha box. The last picture shows some of the mud we went through with no leaks inside the box. I use the tab intended to mount a flag to hold the padlock while I'm out on the trail. Keeps it readily available to lock the box when I stop for food and fuel.[/QUOTE. ] If I could change one thing on my boxes it would be the latches. I may see if I can swap them out for some like yours. I don't think they had rearboxes in mind when they designed our rear fenders. Ha!