I don't know how this happened, but a couple of my bridge officers now have multiple tier 1 powers. For example, I have a science officer with Jam Sensors I *and* Tachyon Beam I, which are both tier 1/ensign powers. If I put the BO in a station that can have both ensign and Lt. powers, both the ensign powers show up but not the Lt. one.
I don't know if I trained them and it didn't replace the power or this is a game mechanic I somehow missed in beta, but either way, the BOs who have multiple tier 1 powers are preventing me from using the tier 2 powers. Is this a bug, or am I missing something?