‘Still there are examples of T-34’s breaking down during assaults even late in the war (17). For instance the 5th Guards Tank army in 1943 lost as much as 15% of its tanks during its march to Prokhorovka. In August ’43 the 1st Tank army lost 50% of its tanks due to malfunction. As late as the second half of 1944 tank units tried to replace engines with more than 30 hours of operation before a major attack.’
It seems the 15% figure was not correct. The 5th Guards Tank army actually lost 31.5% of its tanks during its march to Prokhorovka. Superior Soviet engineering FTW!