Fusion
I don't know if this has been happening to all of my other locks (when sketching), but currently I am in the middle of a design and I am trying to draw a rectangle from one point to the edge of another circle, however the blue cross that appears is not on the circle and instead on a different, black, line near it which I never made (the circle I made is blue). This also occurs when I try draw a line between a different part and the circle too. I haven't tested it on other parts though. I am 99% sure they are on the same plane, as when inspecting the plane I made the circle on and the plane I am trying to draw the line off of, there is no distance between them. I am also in the same sketch as the one I made my circle in.
(here the black line on the left of the two other lines in a right angle is not mine and what the blue cross locked onto)
Here is a closer up view
Another piece of info: the human eye, or my eye, can only see this when I zoom in super close, to the point where my surface experiences extreme lag.
Update, I have hovered on the circles (there are two) as a whole again and now this has come up:
For the record, the inner line of this ring is the line I was attaching on to, although it is not even the same shape as the actual inner circle
