Footprint Overlap Error : Only some footprints

[itsko]

When I drag a footprint over another, sometimes the overlap turns the unmoved footprint red.
This is great.

Other footprints, however, make no such display, such as below,
where the connector turns ref but the surface mount cap and IC do not:

I know that it’s not just the first item which lights up; see below,
where a surface mount resistor and resistor array both light up:

.

Is this a bug; is something missing in the footprints of the unlit items?

[Seth_h]

It should highlight them all. You can post your project and we might be able to tell what the different is between the footprints that are highlighted and those that are not

[itsko]

Issue determined: A DRC revealed that there was an issue with the IC and the cap — both had duplicate courtyards. Deleting the redundant courtyards resolved the issue : j