The reason for the delay, according to an ISRO official quoted by the Economic Times, is extra caution in the wake of Israel's failed Beresheet landing.

"We saw Israel's example and we don't want to take any risk," the official said. "Despite Israel being such a technologically advanced country, the mission failed. We want the mission to be a success."

But as some Indian media outlets have noted, there's likely more to this story than jitters over Beresheet. Chandrayaan-2 has faced several technical problems in preparation for launch. It was originally scheduled to fly in 2018, until a review board said the mission was too risky, prompting last-minute design changes and pushing the launch to 2019. The changes also increased Chandrayaan-2's mass, requiring the launch vehicle be upgraded to India's more-powerful GSLV Mark III rocket. Then, a configuration problem during drop tests of a Chandrayaan-2 engineering model damaged 2 of the lander's legs.

A July launch would result in a landing after a lunar eclipse on the 16th and 17th. Since both the lander and rover are solar-powered, and only expected to survive for one lunar daytime (14 Earth days), ISRO would likely want to avoid dealing with any eclipses during the primary mission.