According to the available reports, the Russians have been unable to shoot down even a single rocket launched by the quite active Ukrainian HIMARS systems. The rumors suggest that the Kremlin authorities have been furious, as the S-400 turned out to be ineffective against the US-made rocket artillery system - probably that ineffectiveness also extends to other systems of this kind.
The Ukrainian sources suggest that the scandal regarding these circumstances has reached the Kremlin. The rumors include claims that Putin himself is furious about that, but considering the losses that the Russian forces experience, trying to defend themselves with reportedly lethal systems, any furiousness like so seems to be understandable. Although the S-400 has been designed to act against fixed- and rotary-winged assets, ballistic, and cruise missiles, the manufacturer also claims that this SAM system would also be effective when counteracting rocket artillery assets, such as HIMARS.
The Ukrainian sources suggest that management at Almaz-Antey, manufacturer of the S-400 system, is fearing it would lose their jobs. It is even plausible that court proceedings would be launched against the parties responsible.
Currently, following the proliferation of the western artillery assets, the Russian activities seem to have stopped, as the logistical assets, fuel storage, ammunition storage facilities, and gathering points seem to suffer from the ongoing destruction. This stems from the fact that the legendary Russian or post-Soviet air defences remain unable to engage their targets effectively, especially after the western MLRS systems are becoming common on the battlefield.
It would be curious to see what impact this information would have on the export sales of the S-400 Triumph systems - one of the prime products offered by the Russian defence industry, in the high-tech department.