The first thing I would do is call Surly. My LHT had the same exact problem (mostly not shifting to the big ring) and the shop fixed it by replacing the KMC chain with a Shimano. My Wife's LHT did not have this problem. Both these bikes are 26", 50 & 54.

One more thing on both bikes, the Microshift barend shifters bit the dust within 2,000 miles. They developed so much play in them (on the indexed side), they wouldn't shift properly. This was solved by replacing them with Shimano barends. Along with this, they changed out the RD as it would not work with the Shimano barends. I don't know the exact model of the Shimano RD.

This combination of parts worked well (perfectly) until my Wife was stranded when the Shimano rear indexed shifter broke. I was out of town when this happened and never got the full story on it. They had the shifters in stock and replaced it right away.

I have read that people have had problems with the Shimano barends.

Call Surly first and get an answer out of them. You and me are not the only ones, I am sure.

I have already decided my next bike will have a Rohloff IGH with belt drive.