Regarding Observation 6491387 …
Apparently transmitter on the cubesat is inactive since this observation. You can compare waterfall with previous ones, for example Observation #6487084. You can see straight line of signal at zero. Signal on waterfall is coming from second satellite Skoltech 2. They planned to be close together and to transmit on the same frequency.
Observation #6597863 was yesterday. You can see that nothing changed. Compare with Observation #6594461