Alarm triggered by sensor tamper

Hello, Have had Ring alarm since June (4 months) without any issues. Last night at 4:17am the alarm was triggered. Checked all doors and windows and everything was closed. This morning I looked at the history and it said my bedroom's window sensor was "tampered" and therefore setoff the alarm. I checked the sensor this morning and it's set securely. Any ideas why this would falsely trigger? Thanks!