png incorrect size after export

Hi,

Context:
- 5-track project with non-animated titles, imported videos, imported mp3, & imported pngs
- openshot 2.4.4
- windows 10 x64

What I'm doing:
- one of the png has been resized, and moved multiple times using the transformation tool, so the image hides the face of a child in the video, and follows that child's face around when he moves.
- exporting using following parameters: youtube-hd / hd 1080p 25fps / high quality

What goes wrong:
- while previewing, the image covers perfectly the head's size, but after exporting the video, it's smaller and the head becomes visible

Workaround:
- change png scale again to make it larger, in order to counteract the bug's effect. Works, but is pretty random and can be time-consuming if you have to export multiple times to get it right...

Thanks for fixing!