Karcher Sky-high repair costs

Purchased a Karcher vacuum from ITS in May 2023 in less than a year (December 2023) the motor started being very loud after taking it back to ITS to be repaired we were advised "Unfortunately it seems like the filters have not been used as intended, which has ended up damaging the vacuum motor. This will not be covered under warranty." the cost of repairs is basically the same cost as the machine itself which is absolutely ridiculous we were not told about a cartridge filter that contributed to the damage in the machine. Training is done when the machine is delivered however there is no documentation or checklist about what was covered in the session so no way of proving that we were not trained accordingly. Will not be purchasing any more of their products clearly the warranty is just a gimmick and paying for repairs is just another way for them to make money.