at this point, not much I can do without access to what is going on… have been testing yoast/genesis/simple press and other wp themes tonight… all seem to work fine with the title – certainly not getting extra output like that…
couple more shots in the dark…
what happens ifyou go to forum – options – general settings and turn off the page title generation there?
what options do you have set on forum – integration – page and permalink for the integration display settings? might try having display multiple off and display in loop on… and maybe the strict wp api option…
barring that, would need to get a closer look and do some debugging…