After 2 years, one key stopped working. Contacted Thomann, they asked for a video, and then we shipped the product to Germany for warranty reparation. 3 weeks after receiving the Mikrokorg, Thomann claimed "according to our experts the fault is caused by the customer due liquid damage".
However, this keyboard never had liquid spillage or any other kind of damage/fall/etc. Was always used it inside our home, in perfect conditions: no liquids or dust next to it. Nothing that could ever damage the product externally or internally.
Conclusion: when buying from Thomann, be very careful about the advertised 3-year warranty. In our first case of warranty, Thomann found an excuse not to repair it.