I have had this cooker a long time and it's been brilliant. Last year, after use it was washed/dried, put it in bottom of kitchen unit at the back(cold). It developed patches of mould. I washed it off, dried and used cooker again. I then washed it and dried it again before putting it on top of wall unit. However, on taking it down to use today, it has got mould patches inside again. Is there anything I can do or do I have to get a new one ?