Not recognising rings

Ring Doorbell (-2 I think) has recently not responded to some rings - sometimes it works, sometimes it doesn't, can't identify any reason. Battery is good, WiFi is good. We have videos of postmen and delivery/collection drivers pressing the bell but nothing happens - just Motion Detected. Very frustrating to miss these. This has only started happening over the last couple of months - so maybe a soft-/firm-ware upgrade. Any thoughts?? If this continues, we'll have to find an alternative....