In a multi planet game the hot keys for selecting all ground / air units etc do not work as expected. They literally select all units system wide. IMO the select should perform only on the world you are actually on.
If you select all units and want to target a mex on planet 1. Will your units on planet 2 do anything? Or do they stop their previous orders and freeze?
Well herein lies the problem. They freeze... If I have issued a bunch of orders for some doxes on planet 1 and go to planet 2 and select all my land units with the hot key and issue a command, all the doxes on the previous planet freeze what they were doing.
Yeah I figured that would happen. I don't agree with it but you did select all units and not all units on screen. An all units on planet would be a better option to have. On the plus side if you select all units to kill a commander, and then he goes through a teleporter to one of your other planets and then you scout him, then the units will attack him.