NMIPI Kernel Panic in macOS Catalina - possible hardware failure?

I have an x299 build running macOS Catalina that recently starting hard resetting when I open some projects in Adobe Premiere Pro. The panic is always the same - after a project fully loads all media, system CPU usage spikes to nearly 100% and after a few minutes, the computer reboots. The panic thread is always kernel_task and the panic is always:

NMIPI for unresponsive processor: TLB flush timeout, TLB state:0x0

Here's the top lines of the panic report:

Panic(CPU 0, time 259451726817): NMIPI for unresponsive processor: TLB flush timeout, TLB state:0x0 RAX: 0x0000000009000000, RBX: 0x000000000001cfde, RCX: 0xffffff800c60ceb8, RDX: 0x0000000009000000 RSP: 0xffffff8e01ebfe60, RBP: 0xffffff8e01ebfe60, RSI: 0x0000000000000000, RDI: 0xffffff800c60ceb8 R8: 0x0000000000000002, R9: 0x0000000004104d00, R10: 0x000000000000001f, R11: 0xffffff800c60a1a0 R12: 0x0000000000000000, R13: 0xffffff800c60ceb8, R14: 0xffffff800bd36e70, R15: 0xffffff8118cbed50 RFL: 0x0000000000000046, RIP: 0xffffff800be3cd32, CS: 0x0000000000000008, SS: 0x0000000000000010 Backtrace (CPU 0), Frame : Return Address 0xffffff8e01ebfd10 : 0xffffff800be43e3b 0xffffff8e01ebfd60 : 0xffffff800bcbed47 0xffffff8e01ebfe60 : 0xffffff800bd634f4 0xffffff8e01ebff20 : 0xffffff800be31847 0xffffff8e01ebff60 : 0xffffff800be4c6a3 0xffffff8e01ebff80 : 0xffffff800be43e3b 0xffffff8e01ebffd0 : 0xffffff800bcbebed 0xffffffce64c0bf40 : 0xffffff800bd3d7e7 0xffffffce64c0bf80 : 0xffffff800bd3d9a8 0xffffffce64c0bfa0 : 0xffffff800bcbe13e BSD process name corresponding to current thread: kernel_task Boot args: darkwake=0 npci=0x2000 agdpmod=pikera Mac OS version: 19H15 

Here's what iStat Menus records:
https://imgur.com/Qk0BGyp

The red spike is system CPU usage in Premiere before a crash. The blue spike is user CPU usage during Blender Benchmark which runs just fine.

This problem began when I connected a new monitor to my graphics card, a Radeon VII. I've confirmed that RAM passes memtest86 and is good, and I swapped in my old CPU, to eliminate CPU as the source of the problem. The same problem happens on multiple Catalina boot drives which are all good. It's only in Premiere Pro and only with certain projects. I've already tried uninstalling/reinstalling Premiere and it doesn't help.

This machine has been rock sold for over a year and the problem began with a new monitor (now removed from the system). Does this seem like a GPU hardware failure?

What should I do now to figure out and fix this?

Many thanks for your help!