Sadly not the one in Holyrood but the one in Stormont.
Yes, there has been a valid reason until it was shown the the DUP/Sinn Fein executive could work. As Mick Fealty over on Slugger O'Toole points out the announcement that the MPs will not carry on hold Ministerial or Committee chairs in the Assembly came in my home town of Bangor. It effectively means he is also about to remove his wife from the chair of the Health Committee.
So if the DUP can do away with dual mandates after merely a year after resuming a stable and workable agreement with their tersest rivals for the past number of decades what excuse does the MP for Banff and Buchan and MSP for Gordon have left for holding down two jobs over two years after assuming power and maintaining good ratings in the polls ever since?