you can never guarantee that every plugin will work with every other plugin or combination of plugins and settings.
suggest you :
Plugins
Deactivate all but bbpress and see if this fixes. if it does, re-enable one at a time to see which is causing the error.
Themes
If plugins don’t pinpoint the problem, as a test switch to a default theme such as twentyfifteen, and see if this fixes.
Then come back
Thank you for the quick reply and advice.
I have already tried disabling what I thought could be causing issues..but will try re-instating the old version with all plugins disabled. Then see from there.
thanks