Gun shoots with slmost no power at random

Hi,

I have a Nerf N-strike - Accustrike Alphahawk.

The blaster worked well for a few weeks but then It has started to shoot one or two shots per barrel (5 shot barrel) with almost no power. The dart basicaly drops out of It or It flies like one meter away which is not normal. The rest of darts in the barrel then usually is shot with full power again

Does someone please know what to do with it?

Regards

Petr