I think the main reason why 2014 exit polling showed Republicams winning Asian-Americans is because of low turnout.
Exit polls have significant random error and sampling error, especially for small subsamples and for diverse groups. The "Asian" vote is definitely diverse and non-monolithic, and the exit poll numbers will be significantly affected by, for example, including or not including particular Vietnamese precincts in Orange County CA or Louisiana.
People always overestimate the reliability of exit polls.
