VE isn't an answer, it's a diagnostic.
VE is sort of like a microscope, or maybe an amplifier. It can help you "see" whether something changed. That change can be a change in slope, or a change in wind, or a change in the zero calibration offset. It can't tell you exactly which changed but it can tell you something changed. In your case, you suspect that the zero offset changed at the turnaround. VE could (perhaps) help you identify that since a change in zero offset should often be distinguishable from a change in slope, or a change in wind.
VE is sort of like a microscope, or maybe an amplifier. It can help you "see" whether something changed. That change can be a change in slope, or a change in wind, or a change in the zero calibration offset. It can't tell you exactly which changed but it can tell you something changed. In your case, you suspect that the zero offset changed at the turnaround. VE could (perhaps) help you identify that since a change in zero offset should often be distinguishable from a change in slope, or a change in wind.