i Register
In some senses, mishappen is marked as obsolete, archaic. Watch for register when choosing this word.
verb
To encounter grief or misfortune.
To happen through misfortune.
His fearefull friends weare out the wofull night, / Ne dare to weepe, nor seeme to vnderstand / The heauie hap, which on them is alight, / Affraid, least to themselues the like mishappen might.
To happen ill; fare ill.