What might cause tickets to automatically solve or close upon creation?
Tickets can close via the specific trigger action, Ticket: Status > Closed.
To find this information, open up the ticket in question and check its audit trail (Viewing all events of a ticket). When you're viewing a ticket, you can find audit trail details by clicking the Conversation drop-down and selecting Events.
From there, you can determine which trigger fired on the ticket and updated its status. Once you have identified the trigger, you can look for the condition Ticket: Status > Closed.