Ice Maker Overflowing

My 10 yr. old side-by-side Whirlpool refrigerator/freezer's automatic ice maker has started overflowing. It continues to make ice and seems to cycle normally, but during the refill sequence, the water (about 1 cup) overflows into the cube bin below. Here are some observations:

• Nothing "known" had changed externally, prior to this malfunction.
• There is a water filter on the supply line but has never been changed.
• The fill tube is not cracked and rests properly over the plastic funnel in the rear.
• Upon inspection, the mold is not cracked or loose and the seal between the mold and the cam motor housing looks good.
• During a dump & refil cycle, the cam makes 1 full rotation in about 5 min, with the fins resting at a 2:00 position.
• The heating element energizes at the beginning of the cycle, the fins rotate the cubes out of the mold and the water solenoid opens solidly for a smooth flow of water into the mold.
• The total fill time currently is about 25 seconds, but overflow occurs at 15 sec.
• At the end of the fill cycle the water solenoid closes quickly and solidly with water flow stopping almost immediately.
• Using a hand level, the mold appeared level in both front/back and side to side axes.
• There is a small plastic screw adjustment on the right face of the cam motor housing that is visible when the front cover of the housing is removed. I believe it has a two turn span, but any adjustments don't seem to have an effect.

I'm stumped! It seems like a timing issue, but I can't find anyway to adjust the fill time itself or the cycle time as a whole. The water solenoid sounds like it is doing what it's told to do, when it's told to do it.

I remain, perplexed in Oklahoma.