Your sailmaker can advise you on this. Adjusted them to stop the slapping. Consider replacing the topping lift with a solid vang. It's much smarter to take steps beforehand to prevent problems from starting. It is possible to do serious damage to sails in a few bad minutes.
Common causes are poorly executed reefs and sail changes accompanied by excessive luffing.
It's much smarter to take steps beforehand to prevent problems from starting. The smart way to compensate for a small or inexperienced crew is to make sail changes and adjustments before they are necessary. If the wind is rising, shorten sail or reef before the boat is overpowered. Make sure a sheet is attached to the headsail before hoisting it, and that the sheet is through a lead. Better yet, practice reefing when it is calm.