If your refund is short $1,400 then that is because you said you did not receive the 3rd stimulus payment and the IRS has records that show you were sent the 3rd stimulus payment so they removed the $1,400 Recovery Rebate Credit that was entered on Form 1040 Line 30.
Go to this IRS website for your tax account to see if the 3rd stimulus payment is entered - https://www.irs.gov/payments/your-online-account
If you checked your bank account in the March - May 2021 timeframe and there is not a $1,400 EIP3 payment from the IRS then go to this IRS website for how to start a trace on the payment - https://www.irs.gov/newsroom/questions-and-answers-about-the-third-economic-impact-payment-topic-j-payment-issued-but-lost-stolen-destroyed-or-not-received
No. It is user error. You had to enter the 3rd Stimulus payment you already got or you tried to get it again on 1040 line 30. Line 30 is only if you didn't get the full amount or qualify for more.
A lot of people forgot they got the deposit last March - May. Or missed one payment and entered the wrong amount. Then when the IRS reduces their refund and they check their bank accounts they have been finding the payments.
Did you get IRS letter 6475 saying what they sent you? If you didn't get the IRS letter 6475 saying what they sent you then check your bank statements and check your IRS account to see when and what they sent you.
Your Online Account | Internal Revenue Service
If the IRS thinks they sent it to you but you didn't get it request a trace for a missing third Stimulus payment
https://www.irs.gov/newsroom/questions-and-answers-about-the-third-economic-impact-payment-topic-j-payment-issued-but-lost-stolen-destroyed-or-not-receivedYour Online Account | Internal Revenue Service
Did you see these screens when you filled out your return? See Critter's screen shots