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I agree that the problem may be incorrect tension as you wind the film onto the ring. Although winding speed may affect this, the holdback tension from the make-up table has the most effect. Depending upon the holdback system of the makeup table, tensions can vary considerably from the outer laps to the hub when winding from a 6000 foot reel. The other factor that affects winding quality is the relative humidity. Very dry conditions may cause excessive film curl, which can lead to "spoking" or non-circular windup.

Here is what SMPTE Recommended Practice RP 106 says about film tension:
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2 Film tension
Film tension under normal operating conditions shall
be 1.7 N to 4.4 N (6 ozf to 16 ozf).
3 Measurement methods
3.1 A feed or take-up system shall be measured
with the equipment in normal operating mode
after placing 0.9 m to 1.8 m (3 ft to 6 ft) of film
around the hub of the reel and attaching the
other end to a dynamometer. Tension shall be
plotted against winding diameter and shall be as
specified in clause 2.
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I loaded up Bridget Jones's Diary at a slower speed than my usual and it worked like a charm. I took out the centre ring at.. voila - the film stayed in place.

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