Hardware NAND replacement could work but due to the Wii U firmware encryption, there are no known successful attempts. It has been theorized that restore from a good NAND backup could help however, this is not possible by any software method and might never be if the NAND is damaged on the hardware level. There is currently no known fix for this issue. All firmware versions and hardware revisions seem to be affected by this issue. It seems to suffer from Bit-rot but it is not know whether this is caused by a software issue with the firmware or hardware issue with NAND itself. It is currently not understood what is causing this issue but all signs point to the on-board Samsung KLM8G2FE3B NAND eMMC storage. Nintendo also does not service Wii U hardware anymore nor do they supply spare parts. Nintendo did not comment on this issue specifically, other than supporting pointing to their FAQ page with this error code. As a preventative measure, the community consensus is to power on the console every now and then, about every month. The common factor in all these cases seems to be, that the console was turned off for a prolonged period of time. There are various cases of this, both modded and unmodded consoles, as well as partially working consoles but something like Amiibo Settings not working anymore or certain installed game being unplayable to even nothing in system working at all. Reports of bricked Wii U consoles have been surfacing more and more over time, with error code : 160-0103.

Wii console cleaner