I have a similar/same question. TT error message: "Form 8379: Line 15G (Joint) must be equal to the sum of Line 15G(b) and Line 15G(c). Please check your entries for this line."
On the paper form instructions, Line 15G says "Total itemized deductions (lines A - F)", which I interpret as meaning Line 15G should be equal to the sum of Lines 15G(a) through Line 15G(f) which is contrary to the error message.
