Thanks @Justin_Barrett and all, I will apply that second Gmail step which hopefully will work.
I’ve found a further variation on this that may be related - another of my file attachment scenarios also displayed this behaviour - guess I’m just lucky - but the Integromat scenario is different.
In this second case, I’m parsing a file download link from the email message body, then inserting the link into an Airtable Attachments field. This works often enough, but also fails regularly.
Airtable support had this to offer:
That activity in your revision history typically means Airtable was unable to process the attachment. So although it looks like it was uploaded and then deleted, it’s actually the case that we never had the full file. This could be due to the URL not being a publicly available URL (e.g., it requires a login to access), or the Integromat integration is sending URLs in a format we can’t parse.
Would you mind confirming that the URLs you’re sending are upload-able using the UI when you access the base itself? For example, if you click the “+” in an attachment field and select the the URL option below, does the file upload successfully that way?
And sure enough my example URL failed in the Airtable upload tool, even though it succeeds in my browser. I’ll re-engineer my Integromat flows to include an explicit save-file-to-GDrive step followed by the Get Share Link that @Justin_Barrett identified - -hopefully that will cure both my problems!
thanks again everyone for help on this.