What can cause random lacerations on female genitalia to appear?

Unusual problem: When there are certain states of estrogen deficiency, one may experience dryness and chaffing that may appear similar to lacerations. Otherwise, I am not certain what could be the cause other than excessively tight garment wear producing abrasions or trauma from other sources of manipulation. I would advise consultation with your gynecologist.

Lichen sclerosis: I suspect u have lichen planus/sclerosis: ulcerations on the vulva-vaginal areas can occur because of lichen planus/sclerosis, which we don't know the cause--but likely some autoimmune mechanism. It can be sore, itching, irritated, scarring, and distressing to the woman afflicted. These are quite treatable conditions and so i would recommend consulting your doc for an evaluation. Good luck.