Combat robots no longer expire and can be controlled and grouped with the spidertron remote.
Mods introducing new content into the game.
New ways to deal with enemies, be it attack or defense.
If there are two spidertrone remotes in players inventory, Shift + A switches to the second remote instead of robot selection tools.
I was not able to reproduce this bug using the method you described. I suspect something earlier in your playthrough got the mod confused. If you do find the cause let me know!