Apologies for the dark pictures. The event was early morning in-game, and was unavoidable.
After killing this Infected:
The Zmiovka he was wearing
would not allow me to wear it, despite it's condidion being pristine, and my "Head" slot being empty.
A Video of the event in case this wasn't clearly explained: https://youtu.be/6w3usKY5anY
I believe this was reported for 1.13 too, but I cannot find the ticket to append this to.
I've put "Reproducability" to "Sometimes" as I can't be sure this is always, but I think it is with this particular Infected/Headgear combo..