The enemy sprites have a displaced line in Retrocopy. Is this how it should be? In Meka it looks good. But how behaves it on a real system?

Are you talking about the game here?
http://www.retrocopy.com/sega-master-system/wonsiin.aspx

This is a MSX port and uses the graphics modes which aren't quite as supported in the current public build as they are in the next release. It very well could be a bug. The most extensively tested mode for the SMS VDP is the one nearly all the games use, some cycle accuracy testing needs to occur with the MSX/SG1000 games. Though like I said, we've already improved these modes a lot already for the next build.