I'm having multiple issues with the payload fairings in the VAB:
The wrench icon sometimes sticks after the fairing is deleted
When removing a fairing, the wrench icon follows the cursor, and clicking in the air or in the item catalog opens the fairing construction menu instead of dropping the fairing
The constructed fairing does not match what is displayed in the fairing build menu
The fairing build menu frequently reports collisions when there are none
Tangentially related, discoverability of the TOOBs is poor. Nothing about them makes it obvious they are parametric or that they will change diameters.