Goal: Create area buffers around lines using the "Advanced Feature Creation Options->Create Buffers Around Selected Features" with "Combine Areas" checked.
Problem: Some lines which create islands do not create area buffers. When these lines are selected and area buffers are created with "Combine Areas" turned off... the area is created, but when attempting to combine the new area with the original area... the new area disappears.
Hypothesis: There is an issue with combining areas which will subdivide an island hole area that already exists.
Included is a screenshot and a sample project file. If you create area buffers around the 4 lines that do not have areas and attempt to combine the areas... they will disappear. Also, and more importantly, if you select all of the lines and attempt to create buffers with "Combine Areas" selected... it will not succeed.
*Note*, the outside ring is just a scale marker so I knew what range I was dealing with. Not used in the problem.