This could be because of safe-haven flows into the franc due to the risk-off environment linked to the coronavirus.

Credit Suisse economist Maxime Botteron

There is no evidence of substantial interventions by the The SNB, although there could be a few small actions. This is still the seasonal effect, which I expect to settle down and we will start to see clean numbers from the start of February.

Credit Suisse economist Maxime Botteron