Gravel fell on Fence

Hi, here is the bug that I found. Basically, when gravel blocks fells on fences we can pass through it and it can't be broken. It's like "fake" blocks. The way that I found to break the gravel is to break the fences under it so the gravel breaks at the same time. I also tried to place the gravel right on the fences and the bug doesn't seem to happen.

i provide 2 screenshot to show this bug