What I expected to happen is that the villager would trade me the proper reward for a custom player head

What actually happened was it placed the player head back into my inventory without giving me the proper trade offer

Steps to Reproduce:

1. Summon a custom villager such as this one:

   /summon villager ~ ~1 ~ {VillagerData:{profession:farmer,level:5,type:plains},Offers:{Recipes:[{buy:{id:player_head,Count:1,tag:{SkullOwner:Notch}},sell:{id:emerald,Count:1},maxUses:9999999}]}}
   

2. Get the respective player head it wants

   /give @p player_head{SkullOwner:Notch}
   

3. trade with it

it will not use the head and it won't give you a reward