Gooday Dustin,
that's a new one on me, I couldn't see any overlap
Your sketch has already got this warning, "Fail to generate profile, usually because some curves overlap but not exactly."
So the clue is in this message, I have not received this one before.
I have not explored the rest of the design, so my comments herein may not be appropriate,
1) Is there some sort of lock?,
Yes, and this sketch a few of them, coincident constraints will do this, and your spline is tied with four if I remember correctly. To sucessfully move the spline you would need to move the two lines that are constrained to it with the Move selection as a minimum, but they are projected from somwhere else, so that is your reason for the immovable object.
If anything is drawn off the origin it will also be automatically constained to it as well.
2) The error message has to be resolved, but I don't know how yet, will follow the thread to find out,
The profile is not shaded, first big clue, has to be to Extrude it,
in edit sketch, I looked for then obvious problems, that I always check,
a) it is not a 3D sketch, so that is OK,
b) is the "Show Profile" unchecked, and again this is checked and on.
c) the projected lines are not creating the shading either, (they would create three separate profiles if the error wasn't present.)
So now it comes down to how it was created, I didn't find the start end point of the loop, it appears to be a closed profile to me, too.
I didn't find any duplicates, by deleteing / Undo the offending one,
Over to the guru's.
Somethings for you to consider, and I am certainly not criticising
So far you have not made any Components, depending on the "down the track intentions",
if you do need to convert your bodies (for joints, 2d drawing output,) then you should create a Component for each piece you have done so far,
activating it and all the bits and picee for each part will behave, but late for that now, this has nothing to do with your sketch drama, bit it is likely to be part of your future.
Is there a reason your not building the parts in their respective positions. Big reason for 3d modelling in my opinion.
Might help....