Maybe that's the reason for the picture problems with CALIBRE and the ereader:
In the source HTML files every picture has a scaling like this:
<img src="picture1.jpg" alt="" style=" width:287.76pt; height:291.12pt;"/>
Calibre doesn't remove this scaling (tried a couple of options on ... EPUB Output).
Cover never made problems. Reason I guess is that the cover is added later from calibre from meta data without the scaling statement.
So there is to find a quick prozedure to remove ALL image scaling statements in CSS without doing it by hand (which works fine).
ALL images in CSS have a statement like this above mentioned:
Simple search and replace of course doesn't work...