Macbook sd card reader always in read-only mode

Most of the time when I insert an SD card into the slot on my mid-2014 Macbook Pro, it mounts in read-only mode and I don’t notice until I try to delete a file. When that happens, the option to “Move to Trash” is missing. After checking that the tiny sliding switch on the side is, in fact, set to the unlocked position, I consulted the Googs.

I found a page suggesting that when inserting the card, pressing in the card on the side closest to me rather than the display helped. But still after several tries I couldn’t get it work. One part of that possible solution piqued my interest, though. It was the phrase “bad tolerances.”

On a whim, I pushed the card’s lock button only one or two millimeters down towards the locked position and tried again. It worked! Wooo!