Back around 1960 we framed some limited edition prints for a customer. UV coated glass, I believe, was an available option but rarely used in the retail framing market. These prints were framed with regular clear picture glass but rag mats and rag backing with appropriate hinging.
Come Christmas Eve of 1978 we got a call from our customer stating that the prints were not framed to conservation standards and that he intended to sue us. When the prints were originally framed I was 5 years old. When the customer called with his timely call (Christmas Eve! My dad did not have a very Merry Christmas that year.
) I was 23. I don't remember all the details of what happened afterwards but I know my dad settled out of court for $ 20,000 even though he had letters from glass and mat board manufacturers stating that at the time these prints were framed they were framed to normal industry "standards".
My dad just didn't want the hassle and bad publicity that would result from a court case and chose not to fight the case.
So, yes, a customer could possibly sue. People sue all the time for all kinds of warranted or unwarranted reasons.