Recently the brake dash light would come on when the car was first started, followed by the smart city brake malfunction and front radar malfunction warnings. This occurred intermittantly over several days. The warnings worsened, to the point that they remained on throughout a drive. Checked the usual suspects - camera issues re fogged windscreen, etc. Problem soved by the dealer. My brake pads were worn to 4 mm. The wear of the brake pads causes more brake fluid to pass from the reservoir to the lines to the point where it was below the fluid sensor in the reservoir.