Looks like the chart must source its data from GOES 16 with GOES 18 as a backup. GOES 16 came back online around 0005Z at a much lower flux. Looks like the chart just interpolated between the dropout and return. I would imagine someone is on this. I noticed it earlier as well. Kinda hard to hide the biggest flare in several years; and kinda dumb to even try. Unforeseen software issues…that's far more common and happens without any help from humans.