Hello i still face this issue with latest updates of wpForo and Advanced Attachment addon.
I m paying every year the license but now i don't think will do that, i did not benefit from the new updates at all, i also think that i deserve a free license if my issue will be resolved so i will benefit for what i paid last year.
Waiting for your input.
Please note this issue started after 1.2.7 version updates, all versions after this version don't display old migrated bbPress attachments in wpForo, so i m stuck with 1.2.7 version until today.
Hope to arrive at some resolution with your help.
P.s. i will keep the latest Advanced Attachment addon so you check that the issue is still there.