Very smooth filing to refund timeline (paper filed returns)

We mostly hear worrying stories of delays etc here, especially with paper filings, so wanted to post my positive experience for a change.

Mailed through USPS (Priority + Certified): 3/28

Delivered to IRS: 3/31

WMR status "Received": 4/19

WMR status "Approved": 5/2

Refund received in bank account: 5/6

Total time from delivery to refund being credited: 36 days (5 weeks)

Total time in processing (WMR "received" to "approved"): 2 weeks.

Why I'm especially impressed: I wasn't able to e-file this year. My guess is it had something to do with my tax ID changing from an ITIN to an SSN in the middle of last year. I was told I should ideally notify the IRS about this by mail, so that they can transfer my records, but I did not do that, and I was worried they'll find discrepancies during manual processing and my refund will be delayed.

While my returns weren't extremely complicated, I won't say they were very straightforward either. I already mentioned the ITIN > SSN thing above.

Other than that, I'm a non-resident on a technicality even though I pass the residency test, which again could've caused a delay during manual processing. Even though I live in the US full time, I'm here on an F1 visa, because of which I can't be a resident during the first 5 years of my time here.

Also, I've been churning bank accounts since last year, because of which I received quite a few INT-1099 and 1042s forms from banks. I do all my returns myself, and I wasn't sure whether or not to include those in my returns. I know they're not usually meant to be included, and also that I'm *not* liable to pay taxes on bank interest income as a non-resident.

I sent them anyway, just to be safe, but was also worried that it might confuse agents during manual processing -- since those incomes have not been taxed.

I was hoping for the best, but given the above complications was ready to wait it out for the long haul. Pleasantly surprised that things worked out smoothly!