either grind out a ton of levels and hope to get lucky... but in the worst case, you can save edit your stats to stupid levels for just that encounter and turn them back down afterwards just google rpg file editor (should be like saveeditonline.com or something) and the 1st hit should let you upload a save file and manually edit your money, some items, and character stats, just add an even 5000 or something to your main stats, clear the fight and lower them back down... its cheap, and can ruin the game devs intention on difficulty spikes, but if it causes a game breaking bug and its a work-around you can do now i feel it is fair. Also dont screw with variables as it can usually have bad unwanted consequences.