Yeah this matches my experience too. I noticed this in Anki. Some cards are effortless, some take a bit of practice, and some I fail over and over again no matter how many times I practice them.

Anki kept flagging my relatives birthdays as "leeches!"

I found it kind of hilarious and infuriating that the software I used to remember things tells me "this thing is hard for you to remember so you should just give up."