User addition failing due to invalid generated ExternalContactId?

API Endpoint(s) and/or Zoom API Event(s)

We have been running a sync tool daily using these contact endpoints for >6 months. I have seen only two instances where creating a contact has failed, and even then it’s once-off. On the next attempt the user is created succesfully.

I receive an error response with status code 400, and the following content:

{"code":400,"message":"Invalid parameters: -XMYI6_WSrayjlehht0WZg."}
{"code":400,"message":"Invalid parameters: -7JOmXz5QRWgZln0GkWSVw."}

This “invalid parameter” looks suspiciously like the ExternalContactId which is returned by Zoom. I am certainly not sending anything that looks like this. So I’m wondering, is Zoom generating IDs that fail? The first pattern I looked at was the leading hyphen, but I’ve seen successful responses with a leading hyphen in the ExternalContactId.

I cannot find an instance of a successful addition where the ExternalContactId ended with a trailing period (I only have 70 successful additions in my last 2 weeks of logs to compare against).

How To Reproduce
I cannot reproduce this. I am sending a very simply contact addition, in the format:

    "Name":"Doe, John",

As stated above, the same request works on the next attempt.

Happened again

{"code":400,"message":"Invalid parameters: -pECPRH8RcmidttoMgWxpg."}

And again

{"code":400,"message":"Invalid parameters: -LBjgYlTTa2-ayr8yrna-A."}