Issue with My SSS Silhouette

I bought this new about a year ago, and have been very happy with it – the feel, quality etc.

Except one problem has arisen over the last couple of weeks and that is that when I strum a chord more than very softly: the B string sounds particularly and intrusively twangy and seems to override the sounds of the notes on the other strings.

I wondered if anyone had had a similar problem and if there was a fix?

Any advice gratefully recieved.