Did you file a Joint return?

A $6000 refund is not the rounding error I was talking about, it is most likely you entered one of your W-2s incorrectly.  Double check them or delete the W-2s and start over.

Yes.  What Code is in box 12a?  You might have picked the wrong code.  Don't confuse the "a" with the Code.  That is just part of the box 12 label.  There should be a separate capital letter code like D.

Turbotax seems very sensitive to rounding issues this year.  Suppose your social security from job A is $2000.51, rounded up to $2001, and your second job is $3000.51, rounded up to $3001.  That makes your total social security $5002, when it should be $5001.  This seems to trigger an error this year.  Try dropping your box 4 number on one or both W-2s by a few cents so it rounds down instead of up.  It won't affect your income taxes and the IRS is unlikely to care about a $1 difference.

Also, as mentioned, make sure that each W-2 you enter is assigned to the correct spouse, if you are married.  You can get a false "excess SS" message if your W-2s are assigned to the wrong person, making one person look like their SS was over, instead of two people with SS under the limit.