Four of my window sensor show open and they are closed, i have them since 4 year. If i open and close the window they are closed, but only 2 days, then again on open.
First thing to try is change the battery. You don’t always get notified when they get low enough to start having issues.
The other thing is after the 1/10/23 update to Homebase 2, I have been seeing issues with all my sensors changing state in the app early in the morning, but without a signal from the sensor to do so. Expect Eufy is rolling out more untested code to fix something else.
I have given up trying to work with them and am going to replace with Reolink gear. Their coding and testing practices are crap and I am tired of being lied to and promised fixes which just result in more bugs.