Imported circles display as polygons

Hi. I'm using a DXF file from another application that contains circles and polylines. The file opens OK, but the circles are displaying as polygons with flat sides. They have different numbers of sides according to their size. Some have 8, 10 and 16 sides.

DraftSight knows they are meant to be circles because that's what it shows in the properties box when you select them.

Strangely, you can get them to change into proper circles by resizing them a bit. Then all the corners disappear and you get nice round circles. Anyone know what is happening?

Regards, Bob