Poor connection

Hi. My doorbell 2 started with a perfect connection but now shows as ‘ poor wifi connection ‘ . I have done a speed test at the location of the doorbell and it is 135mb/s but the doorbell shows poor connection when checking the app. I can connect all other devices without delay but with the doorbell, it show the poor connection which i worry will cause delay or missed notifications. The rssi shows -77 which i so not understand due to the speeds i can reach at the location, i have even added a wifi extender which has not helped at all. Thanks