The phrase "potential stumbling block" means something that could create problems or difficulties in achieving a goal. It refers to an obstacle or barrier that might get in the way of successful progress. Full definition
But that's not the only potential stumbling block to value - based pricing. (inc.com)
Whether the reunification holds is an open question, as there are a number of potential stumbling blocks — most notably, the need for Democrats to win two special elections for Senate seats that will become vacant in January. (timesunion.com)
Other potential stumbling block in the government's plans are its changes to the so - called pyramidal systems of scientific jobs at public institutions. (sciencemag.org)