I duplicated and ProSeries shows 85% of social security taxable and never changed.

I did what you said, using numbers that you reported and put them in one at a time not adjusting for the IRA contribution.  Reviewed the return to see that 85% of social security was taxable.

Then I put in the IRA contribution and see max is $2,788 so all is matching up as you say.

When I look to 1040 it shows AGI 110K as you state and is showing 85% of social security still being taxed.

Check inputting for some kind of technicality...IRA Ckd when pension.  Husband vs. wife.  Try removing social security screen and then reinput.  It seems like you might have a glitch....

PS--I made over 70-1/2 or under.  That doesn't seem to be an issue.