I would, as a matter of policy, disclose everything I knew.

Lenses are precision optics, until you take them apart. When you took it apart and put it back together again did a piece of dust or sand get on the ring the lens element rests on? Did you verify the lens on an optical bench after reassembly? There are people who would wonder about that. I bought a 35mm Zuiko where the retaining ring was loose and I reseated the lens and tightened... But every time I use that lens and get disappointing pictures back from it I feel like there might be something wrong with it. I rarely use it because of that. If I sold it I would disclose that.

I once sold (tried to sell) a few things on an auction site. Here's a typical example of what I did. I disclosed defects with circles and arrows...

I have a TLR where the shutter release lever was stuck and I broke it one day. I replaced it with a hand-fashioned lever made out of brass. Works just fine. If you didn't know it you would think it was factory spec. But I know... It's a little soft. If you force it it will bend. Then it will have a little less travel. Then you take it apart and ask "who was in here????"