There have been a few instances over the years of clients managing to create dashboards which have orphan lines. These lines are un-selectable and therefore un-removable, they have the same beginning and end point which creates an area of 0. There are normally noticed when:
1) Sections of the dashboard cannot be cut and pasted, including a CTRL-A Copy etc.
2) The dashboard scroll bars show that its seemingly to large, or has a negative X / Y position (extends left or up to far)
These issues are caused by ACX-3730 and ACX-3910, and normally relate to deletion of objects to which lines were anchored, and are undoubtedly repeatable bugs. The only way to fix this is to:
1) Open up the awx file (which is a zip)
2) locate the effected dashboard file in the dashboard directory of the zip, and open it in your favorite text editor
3) The search for key word 'Line', and you will find a number of these entries:
4) the last of these lines refer to the <version>~<x1>~<y1>~<x2>~<y2>, and the error condition is when x1=x2 AND y1=y2.
5) You will need to change it so that this condition is not true for all lines. In most cases its unlikely you will know what the correct coordinates are, so the best bet is to set something like 1~10~10~20~20~, which will leave all lines in the top left corner of the dashboard where they can be deleted.