From L3 today, it appears that some aspect of the DB schema update silently failed. This particular Bigfix instance was upgraded from 9.5.4 (where some aspects of the DB schema remain) to 9.5.5 last spring to 9.5.7 shortly after it was released. The upgrades all appeared to be successful, however they were apparently not fully complete in terms of DB schema.
Normally running the Admin tool does a schema check, updating as necessary. That isn’t properly catching and updating.
If you haven’t upgraded to 9.5.7 yet and care about WebUI, you might consider watching for a resolution to this one. (Otherwise the 9.5.7 upgrade went smoothly for me.)