Sound like a warp to me, unfortunately this is a relatively common issue with old (or even very new) vinyl and happens in storage.
Even though I've handled literally millions of records over the years It's still hard to tell that a record has serious warps without actually putting it on a turntable. Even then a slight warp might not affect play on one turntable and bounce around on another.
Most record sellers (including me) do a visual inspection of the disc, we do not "play grade" as it simply takes to much time for your average record (not so with a high value record). The only records I play grade are ones which show serious visible defects or have the "feel" of a warp (something you can get to notice when you've dealt with as many records as I have).
If you don't hear back from the seller very soon you should go through the official process for a Not As Described claim, if the seller resolves the matter to your satisfaction no harm will come to the seller (other than a loss of money if they refund).
I would have no problem with a seller if I received a slightly warped record UNLESS they try to weasel out of refunding me.
One counter intuitive thing about warped records, a large but gentle warp is easy to notice but often has no affect on play while a small but severe warp is very hard to detect without playing but can make a disc almost completely unplayable.
