There were some scenes that were pretty awkward because he was literally just not in the mood for any of it. When Farrah asked him to sit in the backseat with Sophia, because Soph wanted some bonding time, Simon seemed totally uninterested and Farrah even called him on his bad mood. He wouldn't say what was bugging him at the time, but now he's ready to talk about it.
After the show aired, Simon took to Twitter to end whatever speculation was flying around out there and revealed that his bad mood had nothing to do with Farrah, or Sophia, even though we saw it affecting them the most.
He didn't elaborate, but Farrah did RT his message and really, they didn't owe us any explanation. We're just glad to see that things are still good between Farrah and Simon because we like them together and she seems really happy.