Automatons has become unreliable - triggering at wrong times

I don’t know what has happened, as I have not knowingly changed anything, but some of my automatons have become unreliable. For example, I have a lamp on an automation set to turn off at 18:30, it has been doing this reliably for many months, but tonight it turned of at 18:37, the automation even states that it triggered it at this time and other nights for the last week it has been doing the same, though I’m not sure if at exactly the same time:

Last triggered: 31 October 2020, 18:37

Yet, the automation is set for 18:00:

- id: '1574671262572'
  alias: Hermie's Lamp - Off
  description: ''
  - at: '18:30:00'
    platform: time
  condition: []
  - entity_id: light.hermie_s_lamp
    service: light.turn_off

I have other automatons set to turn off various things ate 22:00 and they no longer work at that time and I’ve been having to manually switch these off, again these have been running reliably for many months until recently.

I was away from home for two weeks and have now been home for a week, so I can’t say for sure when this issue started.

I welcome any suggestions as to what could be going wrong.

I’d check for known issues and if there’s not one open one. Somebody on Discord was talking about something that sounded similar.

Did you solve your issue since then? I’m asking as I think I have the same exact problem…

All my time based automation where working perfectly, but since around 1 month it’s totally random. First I though it was something wrong with nodeRed as all my automation are managed by NodeRed, but then by desperations have created a very simple time trigger automation directly in HA to see if it was only a problem in NodeRed, but not, it also trigger at random time….

Bellow is the very simple automation supposed to start at every round hours, but it clearly says shows that the automation starts randomly between 10-15min later. Some time it is only 1-2 min late, sometimes it can be 50min late….

Core: 2021.9.7
Supervisor: 2021.9.0
All running inside a virtualbox on linux

Your problem is down to your use of a VM. The guest isn’t getting accurate information on clock speeds, so the internal time is wrong.

If you’re not running Home Assistant OS you can install the guest agent (or whatever it’s called).

Thanks you very much @Tinkerer, that would be a very good explanation. But then my problem is how to solve it as I’m running the official .vdi image from HA.

now you say it, I actually did around the same time an update of VirtualBox, and the problem might have started from there. To confirmed the problem I’ve just created a new VirtualBox session with the latest official HA .vdi image, and I have the same issue even if it’s a clean install.

Do you know if there is something I can do in HA OS to try solving this probable issue with the guest agent, or the only option is to try downgrade my VirtualBox?

You could add your voice to an existing issue

Thanks, I will. Has a closing remark I have downgraded my VM, but it didn’t solve the issue. Then I tried earlier .vdi image from GitHub, and I can say now that the issue started with Home Assistant OS Release-6 build 3.