If anyone ends up here looking for an answer here it is - one of the batteries is dead.
Got warranty? RMA (I did and got the battery pack replaced).
No warranty? Buy a new battery pack on Aliexpress.
Whenever I start the vacuum in the highest power mode or switch the power mode above "normal" during an ongoing cleaning the vacuum stops after a minute. The lights on the device are off, there is no connectivity and I have to put it back to the charging station. It doesn't matter whether the...