I've seen this pop up on occasion, still can't figure out how it happens, I've never had a problem, have had my deck since launch and can't even imagine how this would degrade over time based on how it's used, but non the less. I would just spend the $15 because IF something else goes wrong, regardless of the reality or not, that's going to be brought up. Ya, an O ring costs nothing, but believe me, just get the OEM part and move on. If it were hundreds of dollars, I'm with you, for $15 its hardly worth the research and sidestep.
As always, just my opinion, do what you feel is best