Weapon swapping issues on levels of skills

I play with a wand and focus in the slot 1 (primary weapon) with +2 lvl on cold skills.
When I add a staff for the skill "sigil of power" in slot 2 :
1) the suffix (on my wand) +2 lvl on cold skills disappear...
2) the stats on the focus are not taken into account anymore

So, I have to un-equip the staff but the problem with the slot 1 is still present, it's like the slot 1 doesn't work... I'm forced to use my primary weapons in the slot 2...
It's a little frustrating...