I dont know LMB personally but as a leather technician of 10 years I can answer some of these points from a technical perspective.
Products causing colour loss & gloss level reduction - almost all leather cleaners will cause a certain amount of colour loss on unfinished leather. The only leather tehy wont remove colour from is finished/corrected grain (automotive), but since we wont find that in handbags, its to be expected to a certain extent. However, causing dulling of the gloss level - this shouldnt happen on a new bag! If the bag is used for any length of time the leather will 'buff' to a higher shine than originally, so any cleaner will reduce that gloss level back to the original level. Because the higher shine would of been buffed gradually over time you wouldnt necessarily notice it increasing, but when it reduces quickly from a clean it becomes very noticeable.
With regards to poor restoration - there is simply no excuse for that. It's better to turn the job away or advise the client as to what is possible to restore and whats not, therefore managing their expectations. If you tell a client all will be perfect, they expect a new bag back, but if you tell them you may see a scar or blemish, then they can decide whether to live with it as it is or take the 80% or so improvement. Leather repair and refinishing can only be taken to a certain point, as you are repairing a finished article not a flat piece of leather. The repairer has to take into consideration stitching, buckles and hardware, zips, handles, etc and cannot risk getting top coat into the stitching or zip, and so on.
the point I am trying to make is that LMB could only do so much, but it sounds like where they went wrong was in not advising you correctly on what can be done with the repair. I dont know what they write on their product labelling but it should give you clear warnings on possible risk of colour loss (which is normal) and any other risks.
Hope this goes someway to helping clarify.
