In some cases it seems fixable, but is a manual process. Having to take each image from photobucket, convert it then upload and edit the post.
I've just done this one to trial which had photobucket images https://www.the-t-bar.com/forum/9-mgf-tf-pitstop/34219-a-handy-funnel-suggestion#34219
If you can link here any you want me take a look at.