Xfinity land line phone rings once then stops

This started happening a few months ago. As mentioned in this older postings it happens in spurts. Problem was not resolved 3 years ago.
https://forums.xfinity.com/conversations/home-phone-service-equipment/xfinity-voice-rings-once-then-stops/6375822a384cbc5bcf9cfc5a

My Xfinity land line will ring once & stop, and leaves no caller ID. This happens about 3 times within an hour and won’t happen again for a few days. It hasn’t happened for a few weeks & I thought the problem might have been fixed. But it happened again late last night.

Any ideas what is going on?
Thanks