I've noticed in defensive battles the scanner ability of defense platforms doesn't mark enemies.

Noticed that too

Hi yes it's been reported to the devs, thanks !

Fairly certain the devs never played their own game. Yes the scanners don't work (i think this was also a bug in battlefleet gothic 1 which makes it even more embarrassing.)

This is true. I find it comical when you go against an AI's under running silent and you see them constantly pop scanner sweeps when you're close to no avail.