the underlying problem is similar to https://forum.inaturalist.org/t/cannot-access-certain-observations/42451. there’s a user 5639681 who made some updates to the observation but then subsequently deleted their account.
i could probably fix the observation, but the question is: should i?
the observation loads fine if you view it in the website while not logged in. the main difference betwen logged in and not logged in that i can see is that you don’t see who faved an observation when you’re not logged in, and i assume that’s the part that is causing the page to fail to load when you’re logged in. that’s probably something that should be fixed, but it’s such a minor bug, a relatively small percentage of observations have any faves, let alone get faved by users who subsequently delete their observations.