Sounds like they need to increase pay and reduce the number of hours worked while still getting a salary and benfits to entice more people to the position and make the stress more bearable for those they can get to fill the position. It’s not a matter of how many people are qualified it’s a matter of how many people want to make the tradeoffs to work there and be upskilled to meet the requirements. If your deal is not enticing enough, you need to restructure how the position works in order to entice more people for the position.