Unable to edit certain objects on FigJam

Firstly, the community resources are amazing and really helps bootstrapping projects.

I am hoping to reuse some of the flows as part of my workshop here, https://www.figma.com/community/file/1091121383164972764. I am unable to remove some shapes for example in the first slide here:

My guess is that it might be an object pasted from a different source and therefore not all components are editable. Any idea how this can be done or why it cannot be done?

Also to supplement, I tried checking whether the selection is a Group or Section, but understand that it is not.