4 matching tyres, and ideally all of similar wear, will address the traction issues.
I have never had any traction issues with the Sessantas and overall have found them a better suited tyre for the 370 and spirited road driving than the B/stones. Only issue I have is that my rear tyres are down to around 4/5mm of tread and I was thinking of looking just for a pair of rears, but given the prices you can get a set of MPSS for now they will probably be the next to try.