The Army, which reluctantly inducted 124 tanks from 2009, ......Sources said that the Army’s opinion is that while a large number of tanks are not operational due to technical defects, the fleet as such is not combat worthy due to reliability issues. "A number of tanks are not operational currently as transfer of technology (ToT) of several imported systems fitted onboard has not been done," an Army official said.

The Army is surprised that quality issues have started arising even though the entire fleet came into service as recently as 2013 when deliveries ended. Given that the tanks are highly dependent on foreign equipment — 60% of the tank is imported — the failure to get maintenance technology means that the systems have to be sent abroad for even minor repairs.

https://economictimes.indiatimes.com/news/defence/armys-fleet-of-arjun-tanks-face-technical-issues-major-proportion-of-124-tanks-in-service-not-operational/articleshow/47103764.cms