I have noted on multiple occasions over some time now that some blocks are not hacked which, as far as I can tell, should be. The blocks I have observed are:
On the same grid,
Owned by a neutral or enemy faction,
*Not* turned off,
Powered and functional, and
*Not* damaged; or in cases definitely above the functional/hacking line.

There were also a variety among these blocks, and these observations were made among different grids as well. Most recently, all the above criteria were met by a jump drive aboard an NPC ship (from one of several Modular Encounters mods) which was not being hacked. In all observed cases, the hacking computer claims all hacking is complete, or otherwise says nothing.

*Seriously* love this mod, thank you!