or from the changes you have done on wpForo
I created today a fresh new WP-4.9.18 installation and installed an also fresh wpForo-1.6.1 (with absolutely NO customizations at all), no other plugins were installed, and tested the situation. Just wpForo working under default WP Twenty-Seventeen theme.
Unfortunately the situation persists. So this seems to be a bug on this wpForo version.
You "don't support wpForo old Versions." and I understand that perfectly, and also I don't expect this version to be flawless. You have made a wonderful plugin so far and I'm thankful for that.
I will try to find a way to work this around.
Well, that's it for now, thank you so much for your and the support team's help!!