Dirty machines

On 29 March 2021 I bought some roast beef, I asked it to be sliced for me, thick. When I got home I was duly eating it and my partner saw that it had black streaks on the meat that looked like some kind of grease/oil/lubricant, whatever it was it should not have been on the meat. It was uniform in the way the steaks were. Unfortunately I could not retrieve that particularly badly streaked piece of meat. I took the other pieces back, one piece was also streaked. Spar management started to say "no it couldn't be oil/grease/lubricant etc" Now I do know without a doubt that these machines are lubricated as they are metal and I dislike being treated as though I'm some stupid woman - not appreciated.