Welcome to the forum
What discs are you using? The latest problem (only 4x burning) sounds like a possible firmware support problem for those discs.
To help us further diagnose the problem, could you download and run CD-DVD Speed (or DiscSpeed, as the version that comes with Nero is called).
Put one of the discs into your 203B, then go to the “Disc Info” tab in CD-DVD Speed.
There you will find the MID info - please post that for us.