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We report results from our ongoing project MOMO (Multiwavelength Observationsand Modelling of OJ 287). In this latest publication of a sequence, we combineour Swift UVOT--XRT and Effelsberg radio data (2.6-44 GHz) between 2019 and2022.04 with public SMA data and gamma-ray data from the Fermi satellite. Theobservational epoch covers OJ 287 in a high state of activity from radio toX-rays. The epoch also covers two major events predicted by the binarysupermassive black hole (SMBH) model of OJ 287. Spectral and timing analysesclearly establish: a new UV-optical minimum state in 2021 December at an epochwhere the secondary SMBH is predicted to cross the disk surrounding the primarySMBH; an overall low level of gamma-ray activity in comparison to pre-2017epochs; the presence of a remarkable, long-lasting UV--optical flare event ofintermediate amplitude in 2020--2021; a high level of activity in the radioband with multiple flares; and particularly a bright, ongoing radio flarepeaking in 2021 November that may be associated with a gamma-ray flare, thestrongest in 6 years. Several explanations for the UV--optical minimum stateare explored, including the possibility that a secondary SMBH launches atemporary jet, but the observations are best explained by variabilityassociated with the main jet.

MOMO V. Effelsberg, Swift and Fermi study of the blazar and supermassive binary black hole candidate OJ 287 in a period of high activity