Just a few minutes ago, after lowering the CSP to 0.2.0 and then pulling the side_l back down, I pressed SHIFT again to read the side_line and it worked.
By inference from the fact that the yellow line did not appear until I re-drew it, I can conclude that perhaps the side_line I once drew did not fit the current CSP or was broken.
I then raised the CSP to 0.2.2 on the other course and redrew both side_lines, and the yellow line appeared the same way.
The only strange thing is that I only re-drew the side_line and got a yellow line... I wonder why? Well, I'm glad it's fixed.
Thanks for sharing your method, Esotic.