Pitch fibre pipe, common in properties built between the 1950s and 1970s, is particularly vulnerable: it deforms and delaminates under high pressure. If your property is that age, mention it when you book.
Where a pipe is already cracked, jetting can enlarge the defect. This is not really a jetting fault — the pipe was failing already — but it is the reason a camera check before and after matters.
Ask what pressure will be used and whether a survey will accompany the work. Any reputable drainage firm will answer without hesitation.