Intermittent Booting: Stuck at Apple Logo with No Progress Bars

Greetings, iFixIt,

I find myself quite worked up with a boot scenario of an 2017 iMac 4K model (iMac18,2 i5) from a customer, which appears to be similar if not exactly the same as described in this post.

Some of my observations:

1. Power Drain Ritual:

• This iMac exhibits a higher success rate of booting up post a "power drain ritual", which I'd have to disconnect the power cable, let it drain, then rebooting. However, this isn't consistent.

2. Verbose Mode Halt:

• On occasions where I verbose booted with a hotkey, the iMac gets halted at EB|LOG:EXITBS:START. A hard reset followed by a verbose (halt) reboot has, at times, allowed the system to boot successfully.

3. Fan Behavior:

• Upon plugging in the power cable while holding down the power button, the fan spins at full speed, maintaining the same speed even post boot. While the fan is spinning at full during user selection, within seconds, the OS crashes and pops the message "your computer restarted because of a problem", and this loops endlessly when the fan is at full spin.

4. Thunderbolt/USB-C Port Malfunction:

• The Thunderbolt/USB-C ports does NOT work, when booted and opening system information, "Thunderbolt/USB4" returns "No hardware was found".

5. SSD Health Check:

• I took off the SSD, analyzed via CrystalDiskInfo on my PC, it portrays a "healthy" status at 1% health. The main key metrics include a total host read of 97266 GB, total host write of 80078 GB, and a power-on count of 211035 instances over 2519 power-on hours.
  I suppose the high power-on count to be originating from a theory that the previous owner left the iMac powered on for weeks while it was stuck at the Apple logo, potentially racking up the SSD’s power-on count; I imagine the iMac could be incessantly running POST tests while it's stuck at the Apple logo.

6. No Grounding Pin:

• The grounding pin on the power cable is missing, I suppose its ripped off by the customer, perhaps a power surge without ground caused these hardware failures? Though I suspect the power supply itself must've been able to mitigate it in the first place.

7. Standard Troubleshooting:

• I've done NVRAM and SMC resets, reseating internal connections, and updated macOS to the latest version at Ventura 13.6, alas, to no avail.

With verbose halts, fan orchestras, and Thunderbolt ghosting. I'm reaching out to this community to shed light on this.

If you have any information, if at all, please let me know how this could be potentially solved. Thank you all.