I'd suspect something has changed about your thumb or the way you put your thumb in the hole or your release. If you cleared it before, something has changed and either you're doing something different or your thumb no longer fits the hole size, shape or pitch.

Maybe you're knuckling it to hold onto the ball. That's a sign that the hole and your thumb no longer match.

Also it's possible, you just need more or less tape to fit the hole to your thumb. Changing seasons (temperature or humidity) or changing body weight can also be responsible.
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"None are so blind as those who will not see."