BT, you didn't say if you are able to hear sound through computer headphone jack while Tascam is plugged and powered on.

To eliminate any sound driver/ hardware routing conflicts between two devices (Realtek and Tascam) I would temperarely disable Realtek from device manager to see if it makes any difference with glitching.
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Also...My interface would sometimes misbehave when plugged in "hot". Meaning, plugged to computer, when computer is already running. So what solves for me is turning interface On first and then powering up computer.