I have not seen any exact sequence, but when having primary as Sword/Shield and secondary as Destruction Staff (in this case a Lightning Staff), when I switch from the Staff to the Sword/Shield, the Sword/Shield do not show (though the effects and hits still occur). They do not even show in the pause screen. Switching back to the Staff is fine though. I have to change location (through a door, wayshrine, etc) for the Sword/Shield to show again.
PC/US, Win10 x64, GTX1080, driver v418.91 (though it occurred with the last couple of drivers as well).