Deductions & credits

Check your K-1 entry, in particular the "Other Situations" screen.  On that screen, make sure you checked the "I personally paid health insurance..............." question.  When you check that box, on the next screen you will get a box to enter your Medicare Wages (box 5 of your W-2) from This S Corporation.   Don't enter the medical insurance premiums, they are already in TurboTax from your 1095-A entry.  When you enter your W-2 box 5 wages in that box, your self-employed health insurance deduction should calculate correctly.

Here are the screenshots of the TurboTax screens you are looking for: