ToME: the Tales of Maj'Eyal

The 'Arrow Echoes' skill of my character only fires
2 arrows in 2 rounds instead of 4 in 4 rounds.

Does anyone have an idea why?

the duration scales with paradox. notably when you drop below 300 paradox it very quickly becomes 2 turns.

this is one of the few TW skills whose efficacity is impacted a lot by paradox, another is Invigorate.