First off, I want to apologize for the delay in getting back to you on this issue! Based on what you have described, it does sound like there is a case where some specific data is causing the system to trip up when creating a campaign. In order to troubleshoot this properly to determine the cause, the best course of action would be to send an email in to firstname.lastname@example.org with as much of the following information as possible:
Email addresses that threw the error
Request Payload that returned an error
Date/Time of errors
At this time, I am not aware of an issue that we know of which would cause this behavior, but we definitely want to investigate on our end to make sure that things are working correctly.
If you do have any additional questions, please feel free to ask them here or to reach out to us by email!
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