Costco Kirkland Signature 312 batteries draining quickly

After Costco batteries dying after a couple of days, and recently after only 4 hours, I took a very close look… corrosion around the battery, as well as on brand new batteries in the still sealed packet. What is going on there? Those batteries were dated good til 2026. My new Widex batteries lasted a week, no problem.

Could it be storage related? Costco will take the batteries back, though they might want you to have at least half the quantity left (don’t think it’s official Costco policy)

Don’t want to risk damaging my hearing aids with corrosion, solved the problem by getting a box of PowerOne 312s from Amazon… always had good luck with these in the past, and no child-proof packaging.

I recently purchased a box of 312 batteries - Kirkland Signature - in a child resistant packaging. However, I cannot open the plastic casing. I am instructed to “cut dial to access battery”. What is the “dial” and how do I get the battery out of its casing? A little help would be appreciated.