I was noticing this for teh last few builds, and a co worker is having this issue as well.
i believe it started around the time that "Processing Maven Resources" feature was added. essenttailly, resources are not being copied to teh output directory all the time. we then get class not found, or file not found when the app starts up and tries to read config. Clicking run again, seems to "kick" idea, and it then takes a few more seconds to actually copy resources. something strange is going on...you probably want this fixed before the official 8.1.1 release. This is all interesting, because prior idea versions did not clean out the resources output so aggressivly - what i mean is that i can NOW do 2 runs in succession witth no code changes, the first succeeds, and the second i have to click run twice to get the resources copied. but...the resources were there a minuteago for the first time i clicked "Run"!!
additionally, i am noticing libraries "dissappear" from the module config, and i have to maven sync again to get it back.