[GeoffR]

The line endings in the CSS file make no difference, it is Calibre that reads the CSS file not the Kobo device.

Perhaps you could find a small public domain book that has the problem, and post a copy of the KePub that Calibre has sent to the device, i.e. use calibre to send the book to your device and then copy it off the device and post it here.

Also you might post a screen shot that shows the problem, it could be that we are talking about different things (e.g. there is another problem that affects KePubs where the text is cut off at the bottom of the screen, that problem cannot be fixed by CSS.)

In the end there is always the option of sending the book as an ePub. ePubs don't suffer the cut-off problems that afflict KePubs in full-screen mode.

Edit: Of course it could be a new bug in the new firmware too, I am not running the new firmware, but if you post a book I could test it on the old firmware to see if the problem is the book or the firmware.

Edit2: Also to note: there have sometimes been problems that occur if you switch between normal reading mode and full-screen mode from within a book, it is best to exit the book, switch reading modes, then open the book again. There is also a KePub bug that started in the 3.19 firmware where the margin slider stops working, for which the work-around it to exit the book and open it again. None of these problems seem to affect ePubs though.