Rheinmetall AG’s position as the standout European defense stock is looking increasingly vulnerable after a series of disappointing results led a long-time bull to downgrade the shares.

Analysts at JPMorgan Chase & Co. on Friday cut their recommendation to neutral after advising clients for nearly four years to overweight the stock. They also slashed their price target by almost 30%, citing a greater risk of earnings downgrades than upgrades. Shares in the German manufacturer of ammunition and tanks fell as much as 6.8%, extending year-to-date losses to almost 20%.