Franke not honouring geyser warranty

Franke geyser replaced in 2019 under warranty, with a new geyser with a 5 year warranty. Now 3 years later the geyser has cracked again. Franke refusing to reimburse stating that the geyser is only under guarantee from the 1st geyser installation date. How do you replace a geyser and then says it falls under the previous, broken geysers guarantee date??

I will report this to ombudsman