Mac Mail (iCloud) - PDF 'Corruption' Issue

[oldmacs]

Hi there,

I have a family member using Mac Mail (M4 MacBook Air, MacOS Sequoia) with an iCloud Mail account - some PDFs attached to received emails will not open properly.

• (Mac Mail) Opening into Acrobat (default) brings opens some of the PDF, but missing the body and Acrobat Displays an Error.
• (Mac Mail) Opening with Preview results in a mainly blacked out document with a few sections of text.
• (Mail Mail) Quick look has the same results as preview.
• (iCloud Mail Online) - the PDF downloads and opens absolutely fine in either Acrobat or Preview.
• (Outlook New) - The PDF previews and opens absolutely fine as a quick look, Acrobat or Preview.

Forwarding the email in Mac Mail results in the same issues when opening the forwarded attachment in Outlook & iCloud Mail Online.

Have tried synchronising the folder, rebuilding the mailbox, quitting mail, restarting etc with no difference.

Has anyone seen this behaviour or could suggest a fix?