Hi Eric,
Sorry you’re having issues.
This sounds like it might be a graphics card issue or some kind of bug (yes I know it’s a spider)
If you are sure that the bones are selectable – try this…
– jump into local view of just the armature (hit / ) and see if you can select the offending bones
– try disabling the selectability on the .geo collection
– check that “Edit > Lock Object Modes” is disabled (although this should only make a difference if you are selecting the mesh as well
– Also try holding alt and selecting the control (this should bring up a selection menu)
Also I don’t know what version of Blender you are using – but see if you have the same issue in 4.2 LTS and 4.5 LTS.
My thinking towards the graphics card issue is that maybe the gfx card thinks those parts are actually behind other things (even though they are not) and it’s telling Blender that you can’t select something that is behind something else.
(also try the alt select trick while positioning the viewport so there are multiple bones overlapping – see if the bones show up in the list)
