Do you remember if the packet with the unsupported DeviceTimeReq MAC command still make it to the application’s Data page in TTN Console?
(If it did not, then that might explain Cannot see data in device dashboard, while OTAA works and uplinks show in gateway's traffic - #11 by arjanvanb. But given the empty default in the code I’d assume that unsupported commands would just be ignored. It should then probably stop processing subsequent commands too though, as for unsupported MAC commands the server would not know if those provided any payload for such command; issue #748.)