I have only had one real problem over the years, but based on that I would suggest you should always assume the worst.
I had a PCP that I terminated after paying over 50% (wife dumped her car on me as I paid for it when she wanted something awful/new and I didn’t want her old car - also the last time I paid for her car). I took video/photo’s and copies of all the docs they insisted were returned including getting a replacement copy of the MOT certificate, I literally made sure it was exactly as required. After handover I chased them once for confirmation everything was in order and heard nothing, 3 months later they came back demanding north of a grand for ‘damage’, missing paperwork, parcel shelf, spare wheel, toolkit etc.
I can imagine this may work with some people who are willing to just pay them to go away, especially if they will take a reduced settlement figure to ‘avoid legal action’, the call centre doing this seemed to have multiple agents doing the same thing from what I could hear. The call lasted over an hour and despite advising them clearly at multiple points that I had no intention of paying them anything without an invoice and pictures showing the alleged damage, they were instant that they would be passing the ‘debt’ onto a DCA for ‘enforcement’, something that they can’t actually enforce without taking me to court and receiving a judgement, though they could get a DCA to threaten to do exactly that. Eventually when it became clear I wasn’t going to cave, and the advisor refused to escalate the call, she went off to instruct the heavies and I sent a recorded delivery letter with copies of the photo’s, a transcript of the call and a link to the call audio and the video of the car with a covering letter explaining as I had no invoice let alone evidence provided to me, it wouldn’t be paid and if they did want to take me to small claims court, I had very strong evidence showing the claims made were false, I would also have the hearing moved to my location and counter claim for costs/loss of earnings - ironically HMCTS were one of my clients. I also suggested that while I welcomed my day in court, it appeared that they were potentially attempting to obtaining a pecuniary advantage through deception, which falls under criminal rather than civil law. It took them less than two hours after they received the letter and viewed the video/listened to part of the call before they called me and said I would have a letter the following day confirming they would be taking no further action.
The other three leases that we have returned since have been totally painless.