I’m not sure how many people here use Tascam US-122 and the US-122L ( I have a 122 and love it). It came to my attention during some recent kernel testing and a subsequent Google search that somewhere along the line after Kernel 3.6 there is a bug in the Kernel that breaks operation with JACK, the device will initialize as normal and will appear as expected as an ALSA Device. Starting JACK brings things to a screeching halt and the server will not connect and error out. This has been observed across various distros. So if you record with a US-122 I suggest not upgrading your Kernel past 3.6 until this gets addressed by the upstream Kernel devs.
Further reading: https://bugzilla.redhat.com/show_bug.cgi?id=902049