It's not feasible to answer such questions by email, or in text, if at all.
The best practice for art is don't work backwards. Start with art, finish with art.
The problem is, graphics software is no better at fixing art than it is at breaking it.
A drawing can become fragmented by simply reducing 5 decimal places to 4.
How to correct any such mistake after the fact is not a drawing or artistic problem, it is impossible, there will be distortion, if not mistakes
I can only say what I usually do, whether that is the best practice is a matter of opinion.
I pretty much never ever try to repair images. I find it better to redraw everything, like I want it, without errors. I don't know any other way. Software can break and distort art at the speed of light. It can only create (or repair) art at the speed of sound, at best.
I mostly avoid broken image problems, so I don't know what to recommend for cleaning up broken images.