When Nintendo pushed the 5.0.0 firmware update live for the Switch recently, it had an unwelcome side-effect for some owners - the newly-updated console doesn't seem to play nice with third-party docks.
Some users have reported that third-party docks - like those from Nyko - actually brick the Switch once it's updated to the new firmware.
Nintendo has now passed official comment on the situation, saying:
Nintendo (recommends) that Switch owners only buy officially licensed Switch products . . . Unlicensed products and accessories do not undergo Nintendo’s testing and evaluation process. They might not work at all with our game systems, and they could have compatibility problems with certain games, the Nintendo Switch system itself, and other licensed accessories and peripherals.
In addition to this, a Nyko representative has told Kotaku:
“(Nyko is) aware of the issue some Portable Docking Kit owners are facing after updating the firmware on their Nintendo Switch to version 5.0. Though further testing is still required to determine the exact root cause of the problem, we believe it is related to the way the Switch handles AV output for an external TV/monitor while the console is docked on the Portable Docking Kit.”
The message here seems pretty clear - if you have a third-party dock, stop using it for the time being. We imagine that the root cause of this problem will be discovered and fixed eventually, but for now, it's not worth the risk.