Okay, signs can be placed against each other and if you break the initial one the all break
Apparently banners do it too if they are placed against each other similarly to signs rather than being placed on their own blocks like normal things.
MC-63834
Banners acting like signs (not sure if bug)
Resolved
Invalid
0
I'm not sure why this is a bug. When you place it on a banner, and that banner is removed, it pops off...