Deleting part of a drawing deletes the whole drawing

I have a line drawing made with the brush tool. I select a part of the drawing, hit ‘delete’, and the whole drawing disappears. Same thing with copy/paste. I select a part of the drawing to copy. When I paste it, it pastes the whole drawing. Any ideas on why this is happening?

I just wanna ask some questions:
are you on the camera/drawing view when you hit the delete button?
is your drawing grouped?

I think there are two most likely causes of your trouble. 1. Another window might be active the moment you hit “delete”. This happens if you are on “Focus on Mouse Enter” on the General tab in Preferences. 2. Your drawings are grouped so if you select one part, you select the rest of the group.

Possible solutions are : make sure you are on the same view/window upon selection and deletion. A red box will help you indicate which window is active. Better yet, uncheck “focus on Mouse Enter” in your General Preferences tab. Also make sure your drawings are not grouped. If they are, simply select the drawing group and press + G to ungroup them.

Lemme know if any of these is your case.