External SD Card Detected, Files Not Showing
You say:


  Also, on a side-note, it says that the phone only supports a 32GB SD,
  but I have a 64GB inserted and it works just fine, seemingly. Could
  that also be it?


Yeah, seemingly. Did you expect anything different?

Could that also be it? YES, with surety above 90% for me.

You appear trying to kinda 'cheat' your manufacturer, by using a size your phone doesn't support on paper. Perhaps, that's affecting the consistency of displaying the contents on your phone. For some phones, like Sony Xperia Z2, the storage won't show up at all if it goes beyond the recommended size limit on paper.

Instead of trying to go beyond whats recommended on paper, kindly stick to 32 Gig storage or less, as your manufacturer says. If it doesn't work, then there's a problem. Until that, you're just messing up with phone.

If sticking to 32 or less storage capacities, the inconsistencies exists, then you might consider:


Trying your SD card in another phone to see if it works. If it works...
Try a different file explorer on your phone.
As a fallback, it might be an OS issue, and perhaps fixed in an update. Update your phone software.