I have been having this issue for a while now. And it doesn't seem to matter if it's legendary or "classic" mode. Actually, one thing that works sometimes, [i]-though it is massively tedious and frustrating-[/i] is to rage-quit with alt-f4, then restart the game. [i](I'm aware that quitting the normal way would probably achieve the same results, but oh well.)[/i] The only problem with this method, [i]-aside from how annoying it is to start back over by Finch, then have to ride all the way across the map and pick up at the last check point, just hoping that it worked, and I won't have to do it again-[/i] is that it usually only seems to work for the very next hive ghost, then starts happening again. I've tried everything that I can think of. Making sure all programs that might, possibly, be interfering with the keyboard, turning off overclocking, even lowering the graphics quality. Nothing works. Once in a while it will start working again, and it will be fine for a while. Then BAM. It starts happening again, and resetting the game only works for one hive ghost encounter before it starts happening again. Even worse, sometimes this doesn't work and there's just no making any progress in whatever quest I'm on.
Sam thing happened to me trying to kill the Lucent Wizard on “The Investigation” mission. I killed it 5 times, ran up to finish the ghost & the finish action wouldn’t come up. Super frustrating. Also on legendary.