I have a Moto G (2nd generation) which stops seeing the microSD card.

[RevvyP]

It works when first formatted and lasts about a week - then the phone can't see the card.
It does not seem to matter what size card I use as an extension to the internal storage - the same thing happens.
The only way out is to get it to forget the card and lose all the data - and start again by reformatting.
You can't access the data on a PC either as it has been formatted only for the phone.
Android 6 latest available from Motorolla Build number MPB24 65-334-3

 

[davidcburton]

I have the same problem, I have had to factory reset a few times, it has twice been sent for repair, 2nd time report said they replaced screws. I have heard about other people having problems with the card reader.
I went through 2 sandisk cards that the phone continually threw out and I now changed the make of card and the problem is now [app] has stopped working which will flash up over the top off whatever else is open at the time.
I have had to put fb and messenger back onto internal memory which is already full of the usual bloatware included with the phone (no offense to those that do use it but personally I have no requirement for the Korean keyboard) & then there are the apps that do not give the option of external storage. I am up for an upgrade in April and cannot wait.
Don't get me wrong, I like my Motorola but it is let down by the SD card reader, I was refused a replacement as this one had not had enough repair attempts, I have found it easier to reset and it works for a while then repeat.