I frequently import DXF files into a sketch of a part. Many times I get a very cryptic message:

Warning: The sketch has not been updated because solving it would result in invalid geometry (such as a zero-length line). Consider:

*Deleting the invalid geometry

*Changing relations or dimensions to eliminate the invalid geometry.

When I look at the sketch sometimes there are entities that are highlighted red and sometimes there is no apparent error whatsoever. If I find something that is red, if I delete it then something somewhere else turns red. This seems to go on until the very last entity is gone. If there is nothing highlighted red then I don't do anything.

How can I get this problem resolved so that there are no errors in the feature tree?