...getting same repeat errors across multiple groups (2 of) with photo uploading not performing:
Not sure that 2 groups counts as "multiple" but did you try uploading a different photo or just the one you referenced as an attachment? In other words is the problem related only to this photo or to others as well?
Another thought; the URL of your "failed upload" may be longer than Groups.io can accommodate. There must be a limit of some sort but I have no idea what it might be. And another... Groups.io might not like uploading material from an "external" site; "not like" as in refusing to do it on principle.
