Magical weapon effects won't trigger

I think this is a bug, but it also might be a mechanism I don't understand.

I've tried several magic melee weapons with bonus effect that never trigger. These weapons were equiped by Seelah.

For instance (among others):

Abrupt Force

Once per round whenever this +1 cold iron scimitar lands a hit on an enemy, the target must pass Fortitude saving throw (DC10) or become stunned for 1 round.

This fortitude saving throw does never appear in the combat log and no enemies get stunned. I'm having the same issue with for example the Marching Terror glaive with the will saving throw and the frightened effect.

Anyone else having this issue? Does the character wielding the it need weapon focus for a that type for the magic effects to trigger?

Edit: I'm only playing turn based combat.