Over at the bogleheads forum people have been complaining about treasury direct for years.
I’ve had an account for many years and never have had any problems although I rarely buy bonds. I use it to check on a few bonds I bought there ~20 years ago and one I bond purchase more recently.
I-bonds you have to purchase there, other treasury bonds/bills you’d be better off buying from a brokerage since many (most? all?) don’t charge any fees. I’ve done that via Schwab, Fidelity and TD without any issues.