Interesting. Did credentials-based authentication stop working for you, or did you just decide to move away from it for other reasons, like the fact that NetSuite advises against using it anymore?
By “oauth” you mean NetSuite’s Token Based Authentication, yes? I would characterize TBA as oauth-ish but it’s different in important ways. (I added support for TBA to our NetSuite snaps.) Yes, you’re correct: you need to calculate a new TBA passport for every request, so you will probably need to restructure your pipeline so that it’s invoking a new instance of the REST Post for each call. Have you tried this?