The error message reveals why it's happening and it's all one problem. Found the problem and fixed it (v1.0.6 above), thank you for reporting it and for reporting these details.
Actually, this '???' is coming from the Filter Thread Fields add-on and is just a server log message, it has no effect but should have been removed.
This has been fixed in the respective resource, thank you for reporting this @PhineasD.
Yeah, most communities aren't businesses, they are hobbies, and many who have no intention of ever buying it will complain about the price too, ignore them. Having developed apps myself both native and webview-based, $100/mo is a steal @Mbx.
Yeah, and Postgres, MSSQL and Oracle support would be valuable to enterprises in particular. Not even IPS has support for these DBs, a rare spot of weakness in a segment where they normally lead.
I don't know of any widely-adopted closed-source forum software that supports any of those 3 DBs...