COLOGNE, Germany — The German army’s upgrades to the Puma infantry fighting vehicle will be late because of problems with the vehicles’ software, the Ministry of Defence has announced.

Officials at the Bundeswehr, Germany’s military, had previously planned to accept an initial batch of upgraded Pumas — 15 copies, according to local military-news website Augengeradeaus.net — by the end of 2023. But alterations to be performed by the manufacturer, a joint venture of Rheinmetall and Krauss-Maffei Wegmann, are now estimated to take until late February, defense officials said.

The Puma vehicles have been something of a white whale for the military here. Meant to catapult Germany’s analog ground forces onto the digital battlefield, their development and modernization has taken years longer than expected.

After a report a year ago that 18 Pumas broke down during an exercise, a ministry assessment portrayed the vehicle as revolutionary but error-prone. Still, the promise of a significant capability leap over the incumbent, decades-old Marder vehicle fleet kept government spending on the program coming.

German lawmakers in May approved a government request to buy 50 new vehicles for more than $1 billion. That is in addition to hundreds of million of euros spent on upgrading the 350-strong Puma fleet to an intermediate and, later, final configuration with the latest digital bells and whistles. That work has entailed improved driver situational awareness, a missile capability and networking features.

According to a defense ministry statement, the delay of at least two months is unlikely to affect core testing and training activities planned for the modernized Pumas. The success of those events, in turn, has a direct effect on pledges made to allies.

For example, defense officials plan to station Pumas in Lithuania, where designs are taking shape for a permanent German troop presence. The vehicles also will be a staple in Berlin’s future troop contributions to NATO.