Is this being dishonest?

[HDMe]

It sounds like you are selling to a store rather than an individual.

IF selling to an individual, absolutely tell them that you have redeemed the digital copy already.

IF selling to a store, then it depends on their policy. I'm not advocating dishonesty... but, for example, a local book/dvd store I buy/sell to has a posted policy that they do not guarantee ANY digital copies as obviously they have no way to verify whether or not they would work.

So you buy from them with the up front knowledge that the digital copy probably has already been redeemed, and you get a surprise bonus if it hasn't!

Selling my used movies to that store, I am not sure if I would make an effort to try and list what movies had redeemed digital copies and what didn't since I know they aren't changing their prices either way and are not guaranteeing them when they resell.