Secured Improved Containers can't store much.
Posted: July 13th, 2022, 8:35 pm
A 600-stone capacity chest, when secured, can only hold around 400 stones. Image as below.
As a temporary fix for anybody facing that problem, manipulate the improved containers' content without securing them, only doing that on the very end, when you don't want to add anything else. Once you're done, then secure them. When you need to retrieve something from the container, you can do it normally. However, adding stuff past 400 stones in any container will currently require that you unsecure it first.
May be a little troublesome, but at least you'll have full use of your improved containers.