Replying to give you some information cause my husband and I reckon its either a specific item in the glamour dresser OR its just total items in ALL your inventories.

I currently have 720 items in my glamour dresser and I do not crash on /isearch

My husband however has 716 items and does crash, but he has maxed out retainers while I have 9 retainers with some of them just half full after the glamour dresser expansion.