I had a unique problem this year. I always grow Walla Walla sweet onions in my EB with great success until this year. The tops of the onions seemed to always be laid down and not growing as high as usual. The EB was in a shadier area (my tomatoes next to it grow quickly and overshadowed) so I moved the box, but it did not make a difference.
Then, one day, I went out to check on my garden and saw my cat "lounging" on the top of my onion EB!!! I shooed him away but I later saw that the onion EB was also a normal part of his walking/climbing path for his shortcut to the yard. So, I finally gave in and picked the onions early. Next year I will try something different.