I thought I could put my 2 cents in this, since I had a Davis Vue installed in Cork, Ireland for 2 years before decommissioning it:
My ISS was installed close to the house roof, sheltered from the main westerly/southwesterly winds that batter the country, specially during winter.
The height difference between the top of the roof and the ISS was approximately 1 m.
During these 2 years, the max. Speed Gust that I recorded was 32 km/h and I can assure you that during this time, there were gusts of > 100km/h measured in the open more than once.
The siting is absolutely critical specially on those countries where the wind blows manly from 1 or 2 directions, otherwise rain totals and wind max. Gusts will get affected severely (There even was a day when I recorded 0.6 mm in total, while the stations in the surroundings varied between 20 and 30 mm. Guess where the wind was blowing from that day
)
I have also experienced the zero values for both wind speed and direction in my VP2: when the wind cups do not spin, the wind direction either shows automatically 0 degrees, or nothing at all.
If I were you, a would site the ISS in the open for a few hours on a windy day and see if you still get those zero values before contacting support.
I hope this helps.