There are two locked frigate shield modules that are locked that don’t appear in the Fleet HQ screen. I think there was only one in 1.15.
This will be fixed in 1.17
They can be unlocked now. When you’re in Fleet HQ, dragging the vertical scroll bar down will not reach the two modules. However, clicking on the down-arrow at the bottom of the scroll bar will push it to the bottom level, where you can see -and unlock- the final two frigate modules.