I've moved this post over to the Server Admin section of the Community where you are more likely to receive a helpful response. I would also consider reaching out to firstname.lastname@example.org as you may be experiencing a bug.
Thanks for posting,
Thank you Diego. I will email support to see if they can provide any clarification.
Ditto happening on our server version 9.0.6. Specifically, this error occurs whenever there is an action URL filter set to mailto: <someemailaddress>?Subject=Something. The datasource we used was an extract -- first from SQL server, then from Excel. Actions were set to occur on 'Select'. Anyone else having this issue or a resolution?