X-ray lightcurves of the impulsive phase of the M3.9 flare. Top: GOES-16 soft X-ray fluxes. The GOES fluxes have been shifted in time to be consistent with the observations at Solar Orbiter. Bottom: STIX HXR count rates in five energy bands: three broad energy bands that are dominated by thermal emission, and two energy bands that show non-thermal emission. The vertical dotted lines indicate the three major non-thermal peaks. A pre-event background has been subtracted from all STIX count rates. The high-energy count rates after the third peak are enhanced due to a detector saturation issue.