iPhone 12 mini is not charging properly with Apple 20W wall brick

I have an issue with charging the iPhone 12 mini. I use the USB-C cable that came with the phone, and I bought an Apple 20W wall brick, so I only use Apple products, no third party stuff. My smaller issue is that if I plug in the charger, I have a 2-3 second delay before the phone starts charging. This isn’t a big problem, I can live with it, but some times, the phone doesn’t even start charging at all. I tried these things so far:

• iPhone 12 mini charging with original Apple 5W wall brick and original Apple USB-Lightning cable works properly
• iPhone 12 mini charging with USB-C - Lightning cable plugged into a notebook works properly
• I’ve tried to charge another iPhone 12 mini with Apple 20W wall brick and Type-C cable and experienced the same 2-3 sec delay
• I’ve also tried to charge my previous iPhone 7 with the 20W wall brick and Type-C cabel, and actually it always worked fine, no delay.
• I went into the Apple reseller, where I bought the 20W wall brick, they tested it with some kind of iPhone 11(I didn’t see exactly which one) and it worked properly with any kind of cable(both original Apple cable and third party cables)
• I tried to turn off optimized charging, still the same issue.

So my thoughts are, it should be a software problem.

The cable that came with the phone can’t be the problem, because it works fine if I plug it directly for example in my notebook. And also, the wall brick should be fine, because as I mentioned, older iPhones are charging without any delay or problems.

I use the latest iOS(at this point iOS 15.1.0)

So, again, the 2-3 sec delay doesn’t bothering me at all, for real. But it was really annoying, when I plugged in my iPhone before going to sleep at about 10 pm, and until the next morning, my phone didn’t charge anything at all. And I repeat myself, it’s not so happening frequently, only about 1 out of 10 times, but still annoying. I don’t want to check evey single time whether my iPhone actually charges, or not.

Is there anybody with the same issues? Is there any solutions for this iPhone-12-mini-not-charging-with-20W-wall-brick stuff?