Franke warranty is not real

My Franke geyser failed on Saturday morning, leaking on the inlet side (suspect corroded through the inner tank and leaking into the insulation, saw visible signs of corrosion even on the outside of the unit). Had to arrange emergency repairs to have water to available for our household by Sunday. Upon removal, the plumber pointed out that there was a sticker of 5 year warranty on it, and that the manufacturing date was only 2017 (meaning it could not have seen 5 years use). On Monday I contacted Franke and they gave me a cop-out response of requiring pre-removal foto of the defective unit, and that since I could not provide this they are not honouring their warranty. I believe this to be an evasive tactic to get out of their responsibility