I have had this happen too on a few occasions. I'm running BIOS 0601. Using Corsair ML Pros attached to Chassis fan_1 and Chassis fan_2. With AIO pump/fan attached to CPU_1. I chalked it up to some sort of random glitch. My temps at the time like the OP, were below 30c.
I should add that I am also using a fan hub (powered) with 3 ML fans connected attached at Chassis fan_2
Other systems in addition to rig in the profile specs:
Aorus Master x570, 3950X, 32GB GSkill c16 @3800, Sabrent PCIe4 1TB, Sabrent 1TB, 860Evo 1TB, 2080 Super, HX1200i, Celsius S36, Define S2, pg348q
Aorus Master x570, 3900X, 32GB GSkill c16 @3800, Sabrent PCIe4 1TB, 860Evo 1TB, 5700XT, HX1000i, H150i Pro, Obsidian 500D, LG32GK650F-B
MEG x570 Unify, 3800X, 32GB GSkill c16 @3800, Sabrent PCIe4 1TB, 860Evo 1TB, GTX1080Ti, SSR-850PD, Celsius S36, Define R6, u3415w