Ergo it is fitted incorrectly, and the converter has failed in his pdi & quality control checks.. As they should of made sure of sealing at close down position.. The gap is clearly noticeable, might be a bent subframe? But then I don't fit these..
An honest fitter, will work hard to put right and overcome any negative portrayal by giving a good customer experience anyway, as its their workmanship at question in the first instance, and not the owners experience, anything else is a crap company..
They have caused the issue, and not the owner.. Anything else, get sca and courts involved....