How to simulate an AC line filter in LT Spice
You could try a small resistor in series with each of L1 and L2 - I use microcap and similar things happen with coupled inductors. Maybe also try a 0.001 ohm resistor in series with V1 too. I don't see anything in particular that would cause a voltage discrepancy but sometimes you have to help the math engines work things out more cleanly with the odd small resistor added.

Maybe you should choose a non-unity coupling coefficient too - try 0.99 (you may have done this of course already)