Hi Alex,
I wish your screenshot would show the X-Sheet as well. I suspect your eye-dots to be on another layer. Is that the case? Or maybe they are on another frame – if you have the light table turned on, you can see the closest frames through your light table (aka onion skinning).
You can only erase lines on the layer or frame you are currently on. So just go to the right layer/frame and erase.
Let me know if this makes any sense?
Best,
Niels