Honeywell DS915 phantom rings

I have been using the DS915s with the Ring doorbell for well over a year. The ring is connected A1 and AC2 and the transformer to AC1 and AC2. This arrangement has worked for well over a year but I now have a problem with phantom rings. The chimes sound but the doorbell has not been pressed and there is no notification on the phone. This happens maybe 2 or 3 times a week. I noticed that the the Ring doorbell is not charging when it happens (the symbol in the app), but the interruption in charging is only temporary. I have checked for loose connections, but I can't find any. However I did find that there was no charging voltage getting to the ring when this happens. I wonder if anyone else has this problem. I see that the DS915s is not on the compatible list on the ring site. Also does anyone know a chime that is compatible and easily available in the UK. I think the phantom rings may be due motion detection occasionally triggering the chime although I have motion notification switched off.