R740 - Fail to post, half power/ fake boot sequence?

I was doing some fall cleaning and powered down the server to blow dust out of the chassis, I do this semi regularly and have never had an issue. I removed the power leads, pressed the power on button a few times and let it sit for a few minutes after pulling it out of the rack. I then used a plastic nozzle and a blower to blow dust out of the chassis. I put everything back together and pushed the server back into the rack, there was some weird resistance that seemed to be from the right rack ear area but I didnt see anything, could just feel it while pushing the server back into its seated position (so maybe something happened to the right rack ear? idk)

When I went to boot it back up, the green power led on the power button didnt light up, but the server started its usual fan ramping, disks booted up and the power and activity leds were lit up and blinking. After 30-45 seconds, the server ramps the fans down and just stays in that state. idrac reports the system is off, even though it went through the weird half powered / fake boot sequence and is now idling with disks on and fans in a low power state. I can shut the system down by holding the power button for 3-5 seconds, so it seems to me that the power button works, but the led doesnt light up. I get the same result when using the idrac gui to power on the system when it is off, and when the system gets to its failed boot state, idrac still shows the system as powered off and only shows an option to power on the server. Trying to power on the server when its in the failed state does nothing physically, but the idrac gui shows a success message.

I dont see anything of use in the lifecycle logs or anywhere else. One thing to note is that the system inventory data is wrong in the idrac gui. It still shows as all my PCIe cards are installed, all my RAM and both CPUs when I've only got 1 CPU and 1 DIMM in with 0 PCIe cards.

Steps I've taken to troubleshoot and get it down to minimum viable boot:

- removed all DIMMs, removed both CPUs and trying 1 at a time, removed all PCIe cards and disks. 

  - Tested the DIMMs and CPUs in another system (r540 and all the components work in that system)

- removed, cleaned and re-seated the right rack ear cables (seen a reddit post that had similar symptoms as me and they had damage to their right rack ear, replacing with an ebay part solved their issue, I have one in the mail)

When there are no CPUs installed it doesnt do the weird, fake, half booted thing, it just stays dead and there are 2 leds flashing on the mobo. I also see in the idrac gui that the system seees there are no CPUs or a CPU is removed, so the mobo and idrac are talking (but the idrac system inventory data is stale).

I have a replacement right rack ear coming to see if that will solve the issue. If it doesnt, the only thing thats left in my mind is that something happened to the mobo and I will need to get a replacement. Which is crazy, but I digress.

I'm here wondering if anyone else has run into this weird half boot/post and the power button LED not lighting up, but the power button works to turn it on and to shut it off (hold for 5 seconds).

TIA!