This bug was fixed in Patch 1.90.358. It is possible that it still occurs for already bugged games.
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. A user on Reddit has found that it’s related to the Vampire pack.
If your save is affected, you’ll see different symptoms, depending on what you try to do.
The only current workaround is to either disable or uninstall the Vampire pack. The pack has the number GP04. This solution only works for existing saves and depending on how much you played with Vampires, it could lead to issue. Do make sure to backup your save before attempting.
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.