I'm not a pkg expert but it looks like the explorer pkg that you want to install is a later version (...126.96.36.199.24.0) then the required pkg dependency, which is is at ...127.0.0.0.2.1.
I would guess that the solution is to create a new BE (for safety) and pkg update the existing BE. Then, try installing the explorer pkg again.
I think there is a pkg update mode that will show the changes that will be made without actually applying the changes. That's another option.