I have pixelmator 2.3 (60714) on iOS 9.3.4 iPad Air2.
When I paste a text layer with a drop shadow and a stroke from my clipboard into an image, I lose the drop shadow after editing the text.
The stroke remains but thedrop shadow does not. If I then drop the stroke, the drop shadow reappears. That is until I turn the stroke back on.
It did not seem to matter which font I was using or the text size.