I do have the same problem with my XT1 Body somtimes.
After usesing several times changing the setting it coms back to normal.
I think it has something to do with the temperature.
I just bought the occasion 14mm F/2.8 and I'm in haven.
What a performance and what a quality.
Complete I would say, The 14mm F/2.8, 35mm F1.4 and the 18-55mm F/2.8-4
What need a man more for in the city? Mabey a 50-140mm F/2.8 ???
I am very happy with my Rokinon 12 mm F2, (same as the Samyang). It's Very sharp.
I miss the automatic shapening a bit
The 10-24mm Fujinon is TO expensieve but most likely better of quality. So be it. Here an result of the Rokinon 12mm / F2