HiHere is longer video. I can try to get dataflash log tomorrow as I know nothing about them. This is not an issue in other Fly Modes, and not really a problem as it's kind of fun.
After reading this I went out to try it myself. My bird does the same. I don't think it is a fault I think that in sports mode it cuts out the motors or almost cuts them out so that people could get a quick altitude drop if necessary in a race. (Of course I could be wrong and we both have Faulty solos).