SO it sounds like it’s a problem with your tascam or your setup.
I just looked at the Tascam and it appears those XLR inputs are mic level. Could that be your problem? if you hook up your KOna card to anything else (like a deck), do you still get the same dropouts?
Are you sure you have hooked up the analog outputs and not the digital?
Most recent drivers/firmware from the AJA site?