According to TASS, in this case we are talking about a Doppler speed and range meter (DISD-LR). The agency was told about this by representatives of the state corporation Roscosmos, which is responsible for the future lunar mission.
The malfunction became known as part of a test run, when the device was unable to show the correct data.
Interestingly, the engineers are not even considering the option of manufacturing a new device to replace the existing one. This is due to the fact that “Luna-25” is already knocked out of the original schedule.
Recall that initially the station “Luna-25”, designed to study the surface of the Moon in the circumpolar region, was supposed to go to the natural satellite of the Earth in October 2021. But due to the need to conduct a number of additional checks, the mission was postponed to 2022.