Splash always had a pretty weird Synchronization Adjustment (SA) option behavior. First of all, why 5 secs limit? You can easily increase it to like 20-30 secs to cover all the needs. Delay increases over time during the single episode and in the end 5 secs is never enough.
For example, a movie can start with perfect sub sync, but later on a minor mistiming might start to happen. Often, when scene changes, this mistiming increases. Very, very, very often 5 secs appears to be not enough to cover the mistiming value. It happens to me with almost every TV show episode, when I have to download subtitles matching the release from another group.