I believe part of your facial nerve also provides part of your taste, not all of it just some of it.
So if your facial nerve is upset it can change taste.
Cyberknife certainly made my nerves grumpy for a while. Your nerves sound like they are grumpy too.
Had this weird headache to half my head for a couple of hours after Cyberknife. In hindsight it was probably caused by my facial nerve tensing weird muscles including weird stuff like glands. After a couple of hours the muscles got tired and started to ache. It went away within a few hours. My hearing and balance also got worse, but that got better over the next 3-4 weeks in particular. and then more slowly after that.
Never noticed a burning smell... But I did notice that if you close your eyes, when the beam comes on that everything gets a little bit brighter with certain beams!
Good luck with the next two treatments