Andrew,
unrelated to any OS or version.

Circles do explode to polylines with two arc segments.
Discussed earlier and very correct because a full circle bulge would be a mathematical limit situation.

When there is no option to 'Undo' anymore or when the file was saved & loaded there is no easy way back.

One of the reasons why I isolate circle entities if I might going to use XP as in the file here:
FS#2155
Even knowing it, I still make more mistakes as I would like. ;-)

It would be nice to be able to exclude circle entities from the GUI explosion action XP.
Can be simply implemented in the top of Explode.explodeSelection with an extra preference in AppPrefs, default =true.

On the other hand, the explosions of circles used internally in various methods should remain.

Regards,
CVH