Single Processing Thread CPU Spike

Hey guys,

I've seen a few forum threads about the "single core phantom CPU spike", but none seem to provide any answers so thought I'd try posting...

Essentially the final processing thread on the CPU meter has recently started spiking and maxing out for no discernible reason whilst all the other threads are either running at about 0-50% (depending on the size of the project). Even when not playing anything this final processing thread is still incredibly active even when all other processing threads aren't. It is also visibly active (2-5% or so activity) even on new projects with like 1 track and a couple of processes. The real consequence of this is obviously Logic begins glitching and eventually overloading the CPU (even if all other processing threads aren't maxed out) and no longer plays the project. See screenshots below for more detail.

The spiking processing thread is ALWAYS the last one on the CPU meter, whether I have 2 processing threads active or 12. 

Switching multithreading from "Playback Tracks" to "Playback & Live Tracks" seems to actually shift some of this "phantom CPU load" to the last 4 processing threads, however I feel this is merely a temporary workaround not a solution.

Changing the buffer size helps only marginally and besides up until a few days ago I had no problems like this.

I have updated Logic and Catalina and all my plugins to the latest updates.

I have reset Logic preferences.

I have reinstalled Logic.

I installed 2x32GB of Crucial RAM, replacing the original Apple RAM. I have tried taking these out and switching the ports they were in, (unfortunately, atm I don’t have access to the original Apple RAM (currently at my parents 100 miles away from the originals)). This has not worked.

I have tried running through my audio interface as well as just the Mac inbuilt speakers.

I didn’t make any significant changes to anything prior to this problem suddenly occurring (the 3rd party RAM has been working fine for about 6 months).

Has anyone found or got any idea what the problem and more importantly solution to this is?

Is it logic, Mac or a 3rd party RAM problem?

System

Catalina 10.15.7

Mac mini 2018 (2020 model)

3.2 GHz 6-Core Intel Core i7

2x32GB Crucial 2667 MHz DDR4

Sorry for the essay!

Screen shots below of various scenarios

Phantom CPU spike, roughly 5 seconds after I paused the track [60 or so tracks]. The final processing thread is continuously at 70% to maxed out.

Same as above but multithreading set to "Playback & Live Tracks". Seems to spread the load but isn't great.

New project, 1 track with some processes, you can see the final processing thread spiking.

CPU overloading, this is running through the Mac minis speakers.

Spiking despite no project even being open.

RAM Info