Is anybody else noticed this?

I cant anymore switch artifact sets using "Equip" button, it says something is missing.

My 2 artifact sets are kicked out back into main Inventory, I switch between manually by removing and equipping new pair.

To use the presets from the artifact inventory, you have to put them back into that inventory. You can do so by using the store all button or right clicking on the individual artefacts. Be aware that the automatic storing of your artefacts only happens if you exchange them for other artefacts. If you just want to put them back into the inventory, you need to manually put them back into the artifact inventory after unequipping. 

I've been using two sets of artifact for months. Now artifacts moved into main inventory, somehow. I did not do this.