Then we know it's not a driver or audio interface issue.
No, recording delay simply *places* the recorded audio at earlier or later positions - it doesn't affect the reception of incoming audio.
If it's just happening in this project, I'm still inclined to think it's plugin related.
As a test, open the project, and remove all the plugins completely (as a test) and try it again. Do you get the same behaviour?
Have you placed any plugins on input objects?
I definitely know it's not a driver issue. It's all worked swimmingly well for the last year and a half. I'll give the plugin removal another try in the morning. It's past my bedtime
Thanks for your persistence.