The SBB timetable app and website can become really unhelpful if there has been an "accident involving a person" [0]; other than that, I've got little issues with them day to day.
But it seems your model doesn't have a way to know that the IC from Biel to Olten goes through Grenchen (it only presents the obvious routes that wouldn't work in this case).
[0]: https://company.sbb.ch/en/railway-development/services-rus/r...
But I've also seen my fair share of "trains in this direction won't recover for hours" over the years, and directly after such an incident, the official systems usually don't really adapt all that well. I don't know if they're "massaged" manually after that or if it's just a case of the entire system finally figuring out that an entire station is FUBARed, not only one or two scheduled connections…