Retirement tax questions

Turbo Tax IS in error.  I completed a substitute 1099-R (form 4852) to put the correct taxable amount on our IRA distribution. It's been rolled over several times and the current institution is unable to correct it because they have no record of our after-tax contributions.  But we do.  On the 1040-SR line 4a is blank, line 4b says Taxable Amount and is the GROSS DISTRIBUTION - not the revised taxable amount I entered on the 4852.  Under the line 4b is the word ROLLOVER.  I have no way to correct it.  Can you help?