I only get a generic lot with a llamacron when planning a mountain excursion instead of the Onsen.
If I choose the lot anyways, I’m taken back to the map instead of the Onsen lot. After that no lot can be loaded anymore. I get an endless loading screen.
That issue seems to be a corruption of the Onsen Lot. It’s unclear what causes them. If your save is affected, you’ll see different symptoms, depending on what you try to do.
There are currently no solutions
In some save games the mountain excursion is still working. If you have the actual bath house as a selection then you can do the excursion with no issues. If you have a llamacron like the picture above, it’s best to just cancel the event.