We have a
force:canvasApp Lightning Aura Component rendering an iframe, and after it's been fully loaded, the normal drag-and-drop functionality on the component within the Lightning App Builder just doesn't work - rather, it just interacts with the iframe itself.
As a result, you can't remove the component from the page, or move it to a different part of the page, because you technically just can't select it (no component level visibility filtering, component property adjustments, etc). Even though the move and trash can icons show up, they're not selectable either (see screenshot below).
The only workaround is to click the component before the iframe has time to load itself, then you can adjust the properties, move the component, delete it, etc. Is this a Salesforce bug or some better workaround? For what it's worth, I only started noticing this issue since the Winter '20 release.