NI Komplete Audio 6 Mk2 - having to set buffer to 2048!

I have just returned to making music after a 12 year break... and got everything all updated and bought a new Komplete Audio 6 Mk2.

The problem is, I am having to set my buffer in both Ableton and Audition to the max at 2048 sometimes or else I get crazy glitching/stuttering.

I know my MacBook Pro is "old," (Mid 2015), but surely it's specs (listed below) can handle this. Each project I'm testing is super minimal. Literally only playing a single AIF file within Audition, and the Ableton set has absolutely nothing complex going on. Ableton project CPU meter says it's only using 3%, and in the main Mac activity monitor there is nothing else significant going on, total CPU load is something like 10% while testing.

The Ableton tone test generator will only go "clean" when the buffer is set to 2048, sometimes 1024 if I'm lucky. 

The odd thing is: If I load up a Reason project that has a LOT going on (multiple FX, loads of samplers and synths all firing at once) - Reason has no problem handling it. I can set the card buffer down to down much lower with no issues.

The other odd thing: if I unplug the NI Komplete Audio 6 and just go default Mac Core Audio out of my 1/8" jack, it can run any of these projects in all three apps all the way down at 64 buffer size. (Ableton test tone runs clean at buffer 64 too)

SO. Is this a bad NI interface? Or is there perhaps an issue with my aging USB 3 ports on the MacBook Pro? (is there any way to do a diagnostic on the ports?)

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NI Komplete Audio 6 Mk2

MacBook Pro (Retina, 15-inch, Mid 2015)

Processor: 2.5 GHz Quad-Core Intel Core i7

Mem: 6 GB 1600 MHz DDR3

GPU: AMD Radeon R9 M370X 2 GB

Ableton Live 10 (10.1.42) (Latest update)

Adobe Audition 2022 (updated)

Reason 10.4.1d4 (build 10,700)(Stable channel)