Inability to Pinch/Move/Zoom on png's attached in Mobile

we have LOVED the new mobile app. Today we’ve found some scenario’s where it doesn’t allow us to see what we need when opening an attached png file.
The file is there, and does open. But we can’t dynamically pinch to move the focus or zoom on the image.
The small zoom ± option at the bottom seems to zoom in on center, but for larger images this doesn’t help when we are trying to see data on the edges of the image.