I based my comment on your original post below.
Cancelling orders because of too much pressure would be a seller not managing their workload effectively, which would be the sellers responsibility, thus sanitizing reviews.
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But, there is also a reason why the order completion target is 90% and not 100%. That's because buyers will extremely occasionally order a Gig which isn't suitable for what they want. But this shouldn't happen more than once in every 10 orders, which will still allow you to meet your target. If this happens to you more frequently than this, it would indicate the seller is not being clear enough with their packages, or isn't communicating effectively enough. Which is again, on the seller. I would say this happens to me maybe once every 200 orders. I target my Gigs at a certain demographic, encourage communication before the order is placed, and explain what I offer and the difference between my packages and what's included extremely clearly.
As with any business you will ever run, you are going to have losses of revenue. If you own a shop, people are going to steal things. If you ship physical products, your merchandise will break occasionally. How you deal with it, learn from it and then implement new working methods in order to factor in those losses and also prevent them from happening again is what's important.
I vet my buyers extremely thoroughly before agreeing to partner with them. Choosing who you work with as a seller is just important as a buyer choosing a gig. Can they communicate what they want effectively? Are they polite? What are their reviews like? Or, do I just get a general bad vibe? If so, I politely decline their order and recommend they find another seller. This will happen in most cases before the order is placed, as 99% of buyers will message you if they've never ordered with you before and you prompt them in your description.
If they fail to message me before the order, and order something which is not within my skillset, or isn't the right package etc. Cancelling the order straight away at least means I haven't worked for free. If I do complete the work, I deliver it. I'm going to be paid for my time, bad review or not. As long as I can prove to support that I've delivered exactly within the requirements, the package and gig description, you should be fine if they try to get their money back.