This happens quite a bit on the .com (desktop version). I'll frequently see the wind lines coming from the SE (for instance), then I'll spot check the forecast and it'll be more than 90° different from the wind lines. This is true where ever I spot check. Not just one spot.
I've tried changing the length of the wind lines, speed, turning them off/on etc. But no joy. Luckily, I don't just use Windy as my forecasting program as 120° vs 240° means a huge difference how bad the ride is etc. And routing as well. 