Strange Gray Rectangles

[Christian221964029d0f]

When I select an asset often times a strange gray rectangle appears. It goes away once I click somewhere else. Although sometimes it will show up even when I'm just playing the animation (not in test mode though) What is this? 

[kglad]

can you select it by clicking it?

if so, tap your backspace key to delete it (after selecting it).

[Nicktendo28]

Click down into the symbol to find it. 

Also check your time line.