I've experienced this numerous times with TOS before. I remember contacting their customer support back in christmas 2013 and they were absolutely clueless. By some miracle I managed to convince them that their numbers were in fact wrong, and they said they would "look into it", however I don't think it was ever corrected. Delta figures were way off, which is scary if you'd use the platform for deltahedging. As a result all the risk graphs were off as well, theta figures were wrong and it was just a mess. After that I stopped using TOS. I went back shortly in march '14 to check some price graphs and they still seemed off to me. This was on futures options afaik. Nontheless, I stay away from everything to do with TOS, Tom Sosnoff or TDAmeritrade like the pest. All completely unproffesional imo.
TOS -> Setup -> General -> Display -> Volatility calculation mode -> Fixed volatility per expiration date Based on how exactly do you trade, this can make your greeks calculations in TOS more usable (if you will use it ever again). I think that default setting is "Individual Implied Volatility", which was not OK for me. In the end I have developed my own option pricing model, with much more exact calculations for my needs.
Thanks, I tried some other vol calculation mode called "Smile approximation" or whatever it was called and still had the same problem. Never tried the "Fixed volatility" thing, maybe that would fix it. Nontheless I have never used TOS seriously for anything, I lean on either the IB calcs or my own spreadsheets...