[Free hand selection tool snaps to a circle]

Something seems to be wrong. When I use the free hand selection tool, it seems to snap to an elliptical selection when I release the mouse. Has anyone else encountered this problem? I'm using an iMac with El Capitan. Did I hit a setting or change something by accident?

[Frequency Separation loses healing tool]

I am very new to Affinity Photo and photo editing in general so forgive me if my vocabulary is limited. I am struggling with a couple of issues. When I use Frequency Separation the healing tool doesn't seem to work. I press Alt and select an area to use as a base line, but when I try to heal an area, nothing happens. It seems to work when I have both the Low Frequency layer and High frequency layer selected, but I'm afraid I'm making changes to both layers when I do that. Could someone explain how this works and why I can't heal a single layer?