Phone is a Moto X Pure Edition, running Android 7, all updates current, battery still lasts several days before needing charge. Recently the SD card disappeared from being accessible. Its a SanDisk Ultra 64GB microSDXC UHS-I with 12GB free (mostly photos). I popped it out, put it on a Transcend USB3 adapter and my PC said there was a file error. It fixed it in a couple seconds and I copied it all to backup. I put it back in and it immediately worked just fine. Then a week later the links for phone contacts and sound files for alarms and ringtones disappeared. I can put them back and then a day later they are gone again. But the music sources still play fine and the contacts come up if I search for them.
Does this look like a failing SD card or a failure in the phone? Any thoughts?