I would go with “allzuregelmäßig”.
Similar to “allzuschön um wahr zu sein”, “allzugroß” etc.
However this is not a single word, but would be split as "allzu regelmäßig" cf. https://www.korrekturen.de/wortliste/allzuoft.shtml
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However this is not a single word, but would be split as "allzu regelmäßig" cf. https://www.korrekturen.de/wortliste/allzuoft.shtml