Operating system: Win 10
Graphics card: GTX 1080TI
Short description of error
Whenever you have data-linked curves and both of them have curve modifiers, only the original curve will deform if you move it in object mode. Check 2,79 for correct behavior (you can have linked curves but they will deform separately). Also, if you have a modifier on a curve, blender starts to draw the original and deformed curve at the same time (which is pretty confusing).
Exact steps for others to reproduce the error
Here's a simple .blend with the issue