The Raspberry Pi uses as disk memory an SD card and for that purpose has an on board SD card slot. The component is badly designed and breaks down easily as many an RPi owner has found out. It is a pity that the card holder is not more robust but on the other hand, the overall cost of the board had to be kept at a minimum.
Anyway, the slot breaks down easily which gives rize to irratic behaviour. Lots of ideas have been posted to repair it and these range from glueing a piece of credit card on top of the card holder to replacing it by a micro SD card holder. None seemed satisfactory to me and I looked for a more robust solution.
It turns out that almost the same card holder is made by Würth Elektronik under the type name WR-CRD. The advantage of this model is that it uses metal to force the card into position and not plastic as was the case with the previous one. The card holder is almost the same because, where the original has two switches the replacement only has the one for detecting the presence of the card. Carefully desoldering the broken card holder and – with slight bending of the contacts of the new card holder to the soldering pads before soldering will have an immediate positive result. It turns out that the other switch for detecting write-block is not necessary: the contacts can be left free (on the photo the top two small soldering pads).
This card holder now already is in function for half a year without problems. I assume it will last “forever”, i.e. as long as the RPi itself!
Note added after repairing the second RPi. There are two issues to take care of: (1) the orientation pins on the back side – made out of plastic – should be removed so that the socket mounts flatly and (2) only the connections to the switch needs to be bent slightly to avoid short circuiting across the soldering pads.