Position related? I'd say no, unless you're getting extreme resonance through the chassis of the 'table. Every time I've had this problem, it's been something along the lines of the MM/MC settings were bumped accidentally during transport.
Also, is the table level? The gradient of the table in conjunction with true "flat" will effect the sound output since stereo from vinyl is modulated at 45 degrees, not 90.
And, not that you already didn't, but check to make sure you didn't bump your anti-skating.