One who turned over his olives [to soften them] and then mourning befell him, or an accident [befell him], or [his] workers misled him, may place the first beam and leave it until after the festival. This is the opinion of R' Yehudah.  R' Yose says: He may pour [the olives into the press], complete [the process], and seal [the barrels] in his usual manner.