I mean it's been racking up the losses lately and the wins in season 4 were because something happened that changed the course of the fight, against Lock-Jaw, Tombstone only won because Ray used the "use your wheels as bait" strategy he is known for, and it would've lost to SawBlaze if it wasn't for the pulverizer separating them. And both Witch doctor and Rotator beat it when Tombstone faced them (although the loss to Witch Doctor was kind of predictable because it only lost to Tombstone in 2015 because it was flipped over). I bet that even if it faces Free Shipping it would lose if nothing happened to change the fight. Think about it, every robot from season 1 have changed at least some since then, not Tombstone, it has remained the same since then and with robots becoming more durable now, it's a matter of time before more robots start beating it in easier and easier ways, I bet Blacksmith could possibly box it in and win because because of its insane durability. By next season Tombstone might end up going 0-4 because every robot will have an anti-Tombstone configuration by then.