For the last 3 days my mode manager which has been working flawlessly until now started switching from Evening to Day for no reason about 1h after going into evening mode and can't figure out why.
Its a pretty simple config so nothing fancy here
.
I tried checking everything and even editing setting and nothing kicks it out of this strange behaviors which now messes with all my other rules and automations.
I don't think that's Mode Manager doing it, just Mode Manager reporting that the mode changed. If you aren't familiar, Mode Manager is just one way to automate changing of modes, but they can be changed a number of other ways: manually in the UI, with third-party integrations you may have set up like HomeKit or through Maker API, with other apps (including rules, etc.) you may have installed, or anything else.
So, I'd start checking there: see if you have any other apps that might be changing the modes, or look into third-party integrations you have that may also be doing it if you have any.