annoying issue: MIME emails always give: Internal display failed; use external viewer? (y or n)

When I'm reading emails with mime attachements, I constantly get this message at the bottom in the minibuffer which throws a wrench into my mail reading flow. Its "Internal display failed; use external viewer? (y or n)" and I have to answer it before I can do anything else.

My emacs info: GNU Emacs 28.2 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.38, cairo version 1.16.0) of 2024-0 6-25, modified by Debian

vm-version: 8.3.x (probably as of two days ago in gitlab, say October 14th?

vm-mime-type-converter-alist is
(("application/msword" "text/plain" "catdoc") ("message/delivery-status" "text/plain" "cat")) Original value was nil

I've been trying to figure out what's making this happen, but of course now I've broken my default setup so it's not working at all. LOL! The basic idea is that all emails which can be converted into plain text automatically should be. But images and such should NOT be converted, nor do I want to be asked every single time.

My current settings are: (setq vm-mime-external-content-types-alist ’( (("image/gif" "display" "%f") ("image/jpeg" "display" "%f") ("image/jpg" "display" "%f") ("image/png" "display" "%f") ("image/*" "display" "%f") ("video/mpeg" "mpeg_play" "%f") ("video" "mplayer" "-ao alsa,oss %f")))

So now I'm trying to strip back my .emacs and .vm files to the absolute minimum to try and track this down. But any suggestions would be appreciated!

John