Exactly one lunar month after the failure of Kosmos 300, the Soviets launched another Ye-8-5 lunar sample return spacecraft. Once again, the spacecraft failed to leave Earth orbit.
When the Blok D upper stage was meant to fire for trans-lunar injection, telemetry readings went off scale and communications were lost. There was apparently a programming failure in one of the radio-command blocks designed to command the Blok D to fire.
The Soviet press merely referred to the probe as Kosmos 305. The spacecraft decayed over Australia before completing a single orbit of Earth.
Siddiqi, Asif A. Beyond Earth: A Chronicle of Deep Space Exploration, 1958-2016. NASA History Program Office, 2018.