As title. This is in 1.5 as well, so you probably know, but I'm reporting for completeness. When hard locked by anything (I just tested with a Tor), the RWR doesn't give the rapid beeping warning. The initial spike and missile launch warnings work, but not the hard lock tone.
This bug should be high on your list, in my opinion. It makes it hard to do anything meaningful in an A-10.
EDIT: I just noticed that the circle around the threat symbol on the RWR display, which should also indicate a hard lock, doesn't appear. So, this is deeper than just a sound not playing.