I took my spare (single) 5-in-1 out of the closet and tested it. Everything in that unit is as-delivered: I have not modified it. I was able to verify that the wind cups do like to stop in one spot more often than others if you spin them very slowly and let them stop. Since they stayed in that spot even when I tilted the housing in the opposite direction, it seems to be magnetic influence rather than an unbalanced shaft/cups. But, having said that, at least on my single panel unit, it takes only the slightest breeze to get them moving again (1-2 MPH) so it doesn't seem to be an issue. Also, I took it outside in the sun and put my ear to the housing and listened to the fan while rotating the wind cups 360 degrees slowly by hand, several times. The fan did not change speed at all as I rotated the wind cups.
So while metal in the housing (whether the motor or the wind speed pickup) might have a very slight effect on the magnet on the end of the wind cup shaft, that magnet doesn't affect motor operation. I have no idea if the dual panel units are different inside and whether those have the motor closer to the wind speed magnet. If so, maybe the wind cups would "hold" more in one position but as nicehelser said, I really don't see the opposite happening: the wind cup magnet affecting the motor.
Mike
That sounds as should be expected.
The resolution of the 5n1 anemometer is 23 cm per second, which is a little bit over 1/2 mph. It seems there's a lower-limit as to what it will report, too. Looking at today's data I don't see any non-zero readings less than 51 cm per second (a little over 1 mph). I've been told the cut-off is 1 mph, so that seems to be in agreement. If there is a value below 51, it should be 28. I'll keep watching for it.
So basically it appears that that the slowest non-zero wind speed the 5n1 will report is 1 mph. By that speed the torque from the wind cups makes any impact from the wind speed magnet inconsequential.