Contacts tagged aren't showing up on Zoom registration list

I’ve been noticing the last couple times my company has ran webinars on Zoom that there is a discrepency between registrants in our system vs registrants in Zoom.

Our process is:

Event registration tag is applied to contact record through action on webpage or in email.
Contacts registration tag kicks off a campaign that passes their information to zoom.
Zoom registers them to webinar.

In testing for each event setup, the process works. What I’ve been noticing for the last couple is that there is a discrepency between 8-15 contacts each event that have the registration tag and yet their information is not passed to Zoom.

I’ve checked the times, dates, etc for when they register and when the info should be passed through and it’s all variable and within the range especially of when Zoom stops accepting information.

I’ve ruled out:

  1. date/time errors
  2. user error
  3. delays in campaign

Does anyone have any best guesses?