I think the glitch is caused by the round plastic bit adjoining the eye sensor.
The eye sensor is situated at the bottom.
After using the camera for a period, the either side of the eye piece (mine is on the left) somehow starts interfering/blocking the eye sensor.
If the eye piece was detachable (like the one on X-T1), you would see what's causing the issue.
Sadly, it can't be removed.
I used a small cracked piece from a cell phone screen protector to stuff the gap.
It's safe to insert anything thin and tiny by using a screw driver to pry the edge of the flexible eye piece.
Enlarging the gap does the trick. ^^