Ice maker fill tube frozen; replaced valve already

Hello,
My Whirlpool refrigerator’s ice maker fill tube has been freezing. The problem originally started last summer. At that time I thawed the clog several times, but it got progressively worse so in August I replaced the inlet valve.

However, 4 months later, the fill tube is freezing again.

The popular advice for this problem is to replace the inlet valve, so could this be the problem again? Looking at the parts diagram on this site, there is no heating element at the tube opening, so I’m assuming that isn’t the problem.

Any other suggestions? I may look into replacing the fill tube; it just seems unlikely that that is the problem since if the valve is working correctly, there would be no excess water in there.

Thanks,
Jason