From what I could gather, the issue is caused by the software the 1099 form provider used to create the .pdf. In some cases you may get a binary .xml or similar file type 'disguised' as a .pdf. The IRS software looks for a metadata file header that indicates the file type is a .pdf; some .xml to .pdf conversion software may not include this.
The layman quick fix: Print out your 1099 (1099-B) in most cases of concern here, from your broker or advisor and rescan it as a .pdf document and use that upload. Most multipurpose printer/scanners can do this or there are numerous free mobile applications.
Turbo Tax can't remedy this (without using the same checksums as the IRS, which is likely their intellectual property) , but maybe they can add their own metadata check to weed it out. Basically the .xml disguised as a .pdf is encrypted binary and not editable for your security (<- makes sense). Just rescan it as a .pdf 😉
