Russians could have hit their own SAM, which was handed over to them by the DPRK

It is likely that the North Korean anti-aircraft missile system was shot down in the Kursk region. However, at first, Russian propagandists claimed that Russian occupation forces had hit a Western-style radar station.
Here's What We Know
The complex was hit by an FPV drone. The images made it possible to partially identify the damaged system, which has similarities to a North Korean short-range SAM: the deployment base, the search radar and the shape of the unit.

Similar silhouette elements of the damaged system. Illustration: War Zone/KCNA
North Korea could start supplying such systems to Russia, in addition to ballistic missiles and artillery systems. This could be a reaction to the significant losses of Russian air defence systems due to FPV drones, precision artillery and GMLRS missiles.
The system was first presented at a military parade in Pyongyang on 10 October 2020. The system was classified as a short-range surface-to-air missile system mounted on a semi-trailer.
However, KODEF researcher Cheol-Gyun Lim claimed that it was only a Lightning 6 radar, not related to the SAM. Other South Korean sources, including the Far East Institute, classified it as a low-altitude SAM.

Comparison of the search radars on the Pantsir and the North Korean SAM. Illustration: KCNA
The system is equipped with cells for vertical launch of missiles similar to the Russian Tor and Chinese HQ-17. The system's radar resembles the Pantsir-S1 search radar, but has other technical features, including the absence of antennas for radio command and control of the missile.
Source: War Zone