As it turns out, the default S7 livery appears to have been mistakenly set to match with Iberia, instead of S7, perhaps due to the similarity of spelling and pronunciation of "Iberia" and "Siberia".
In any case, this addon simply changes the livery to correctly match with S7 A20N flights in live traffic, instead of Iberia A20N flights, and also corrects live traffic flights that match with this livery to not append "heavy" to their callsign. Extract the "OboeShoes_A320NEOS7Fix" folder into your Community folder to install.