Name may not contain the following characters: ' '

Hi, I just faced an error that says, “Name may not contain the following characters: ’ '”
I have 4 layers on the left side of the screen as you can see from the screenshot, 3 of them are ok, but the first one, Layer Slope, has this issue. But there is no ’ ’ in the name. What am I missing?

Unreal Engine version : 4.27.2