I have had no problems with first the 6770, then the 6870 FD shifting on an Ultegra 6800 or 105 5800 series 50/34 chainsets.
Are there any spacers on the drive side of the BB or inside the CW on the axle? Looking down from above the small chain
ring should be ~4-6mm inboard of the drive side BB cup. Is the FD at the right height on the seat tube relative to the
big ring? Without a chain how far out does the FD cage move ie no chain installed, does the FD move out over the big ring
when upshift commanded? Looks like you already posted some of this with your second post.
As an aside, your 6770 brifters will work fine with the 6870 or 8050 series 11 spd Di2 FD/RD. If you ever get the urge to
upgrade all you need are the RD/FD and a cassette. You won't need new brifters.