[Q] Photos not visible in USB > MTP that was visible before. topic

When i first got my One Plus One, I was able to connect it directly and all my photos were visible in the path
Computer\One Plus One\Internal storage\DCIM\Camera

Now when i connect my Phone via USB, I go to DCIM and then it takes a Long long time to refresh and at the end, i see nothing.
Just a Folder called Local Disk and the Windows explorer keeps working (I see the green progress on the address bar)

So today I discovered that if I change the USB settings from MTP to PTP, i get the Camera Photos but nothing else.

Question :-
- Why is this behavioral change ?
- Is this expected ?
- Any way to make One plus one File Transfer Faster ?