BM Media Express Drop Frame from UltraStudio 4k Extreme 3

The setup:
Blackmagic Studio Camera 4k sending 4k 23.98fps signal over 12GSDI to ATEM 2ME Production Studio 4k.
From ATEM, sending signal over 12GSDI to UltraStudio 4k Extreme 3.
From UltraStudio, sending signal over 2 40gbps Thunderbolt 3 cables (2meters long) to 2017 MacBook Pro running High Sierra 10.13.1; 3.1GHz intel core i7; 16 GB 2133 MHz LPDDR3; Radeon Pro 560 4 GB
Intel HD Graphics 630 1536 MB.

The Goal:
To capture the 4k 23.98fps signal on the MacBook Pro on Blackmagic Media Express in Apple ProRes 422 HQ.

The Problem:
After about 5 seconds, the capture stops and I get the error message: "Media Express could not capture the clip. One or more frames were dropped."

The Tests I've done:
Blackmagic Disk Speed Test utility shows my CPU is capable of capturing every codec fine (green check mark by all read and write boxes)
Test captures in Uncompressed 8-bit YUV, 10-bit YUV, and 10-bit RGB capture fine, no drop frame error, playback of the clips look fine.
Tried eliminating the ATEM out of this picture and sending the camera signal straight to the UltraStudio. Same Drop Frame message on ProRes 422HQ.
Tried capturing in ProRes 4444, I DO get the same dropped frame error message as 422 HQ.
Also tried capturing in ProRes 422, ProRes 422 LT, ProRes 422 Proxy, No drop frame message, playback of the clips look fine.
The next thing I'm planning on trying is to re-download and install the ProRes codecs from Apple, perhaps there was an error on install.

What I'm looking for:
Is there a solution to this, or am I missing some piece to this puzzle? I believe I've eliminated the possibility that this is a CPU problem, it seems like it's a codec problem. Can anyone help?

Thanks!

Watch your CPU load (it has to be <50% to have stable capture). It should be fast enough, but nothing is so obvious. If other ProRes modes work fine and 444 not it means your CPU is not fast enough.
Is it dual or quad core?

Looking at the CPU usage in Activity Monitor, the User CPU% spikes to anywhere between 50% and 70%, depending on how long the capture gets before it stops for a ProRes 422 HQ capture test. It stops after about 4-6 seconds. The System CPU% stays at about 5% to 8%.

Looking at the CPU usage during a Uncompressed 8-bit YUV capture, User CPU% is at a pretty steady 11-12% and System CPU% is also at a pretty steady 14-16%.

Since Yesterday, I've also re-installed the Pro Video Formats from the Apple site and tested these captures, still with the same drop frame message result for the previously mentioned codecs.

CPU load is to high. Your CPU is to slow. Check for lower quality ProRes modes and it should be bit lower which makes it working.
Uncompressed almost doesn't use any CPU, so this is correct.