Use Leather Helmet (Dexterity Saving Throw +1) on Lae*zel (Dex Saving Throw +1). Her Dex saving throw still stays on +1
Use Hedge Wanderer Armour (Balance Dex Saving Throw +1) on Shadowheart (Dex Saving Throw +2...why? It should be +1): Stays on +2
So the Saving Throws seem to be calculated wrong with and without items.