Are you not supposed to be able to give any shield?
Then that may be a bug. I constantly gave out shields all willy nilly whenever the opportunity arose to sell a customer a ridiculously high-tier shield even though they were only asking for really low tier.. even been telling people of this possibility, (Not the weapon, The weapon follows what you said and I've been repeating that too, that its can be tier or lower)
Additionally.
You can only give "any tier that is lower" if they're vague
If for instance we look at the pic, and they instead asked for a tin polearm, no extra specification, You can give them any polearm that is tin or copper.
But if they ask for a Tin Polearm with a (something something) small blade and an uncommon grip
They will ONLY accept Tin.
Shields ignore this afaik, at least right now, in 9e
Also I have a few bucks in Paypal if you wanna tell me which choice fits best for that, donate or pay-to-buy, or not Itchio, or whatever.
can't be a patron thing, thou.