I had one of these antenna some time ago and found exactly the same problem.
I complained to W & S and got a refund.
They confirmed that the Watson is infact made by MoonRaker, so that explains a lot in it own right !!

Send it back from where it came from, get a refund.
I use a Chelcom 1/2 wave vert and it is well made and less that 1.4 from 69 to just under 72 mhz.
It has survived over the last 2 years on the mast in all winds and weathers without apparent problem.

Regards,
Tony.

Callsign G4CJZ