Can't Use Headers in Show Thread
There is no button.
The Headers in showthread are pre-collapsed, but there is no collapse/de-collapse button in order to open it up to look at the header or edit it.
This is a conflict with some new Javascript which handles all $vbcollapse items rather than PHP. This prevents the same situation (except more widespread) from occurring if the user has Javascript disabled. Apparently PHP is still used to pre-collapse certain items like the headers in showthread.
Fixed. I have changed the Javascript to only modify the collapse image if it is NOT the collapsed version.