To cut down your project, first do File > Save As to save your project under a new name, to avoid making unwanted changes to your working project. If the project contains multiple flows, delete all flows except for the one that exhibits the problem. If the project contains multiple players, delete all players except for the one that exhibits the problem. If the problem is isolated to a particular bar or passage, then use the Shift+B popover to remove all other bars (e.g. select a note or rest in the bar after the problem passage, type Shift+B and enter a huge negative number like -9999 to delete all of the remaining bars in the flow).