When I look at a sensor, I can see that it’s currently open, that it was closed before, and that something changed 22 minutes ago. But I don’t see that reflected in the timeline bar.
Are you sure the timeline belongs to the same entity?
Also note that a short transition “closed - open -closed” should cause a thin line on a timeline. If it is not there - may be it is too thin and is visible only with a shorter time span.
hm I would think that the state change should have been shown at the end of the bar in that view. What does the History ‘show more’ view look like?
Suggest to create an issue on GitHub.
Also, suggest to use a logbook card (perhaps this called Activity now) for this entity. Then you will have two ways to check a history.
Btw, “last-changed” can be updated on HA reboot (probably not your case).
I suspect you may have a problem with the recorder database or the previous stored data of entity itself.
- Check Developer tools - Statistics tab for the entity if it shows a problem
- Check Settings - System - Log for errors
Another question: did you make recorder settings which entities to record?
I found the cause, sorry for the post.
I had read that Home Assistant can only keep history for a maximum of 10 days.
I had a helper, a variable, that got a value updated once a week. I wanted to be able to look back over a longer period. 52 entries per year didn’t seem like a big load 
But apparently, with the option below in configuration.yaml, only input_number.tapwater_week_totaal_seconden was saved, and nothing else. I expected that only input_number.tapwater_week_totaal_seconden would be affected and the rest of the history would remain standard.
recorder:
purge_keep_days: 365
include:
entities:
- input_number.tapwater_week_totaal_seconden
For now, I’ll monitor it for another 2 weeks with the standard setup, and then I’ll try something like keeping everything for a year and using an automation that checks every day whether saved entries are older than 14 days and deletes them—except for input_number.tapwater_week_totaal_seconden.
I just don’t know if that will work.