@Woodszer I went to my electronics retailer and bought a specification compatible generic one.

and Update from my original post - Still 100% uptime - hasn't had a single problem since replacing the PSU. 

This product is looking like the worst one I could have purchased.  When it works, it works great but ...

It reboots randomly...even after getting a new power supply.  Sometimes 4-6 times a day and sometimes 4-6 weeks between reboots and it's not a question of how much load the thing is dealing with.

It takes one to three weeks after a reboot to add all 102 devices to wireless; the 11 devices connected via cat6 come right back.  During that time, it rejects around over half the packets that arrive at it's WAN port, independent on which device they're headed to....every device sees a slowdown.  I have 16 or so TBs of logs still hanging around here in NAS if someone would like them.  Also during this time, the router showes minor use of the four cores (5-7%) and 38-40% of it's memory.  Around 1/4 of the devices have a static ip, dhcp for the remainder.

What's the deal? Anyone else see something like this happen...and have a way to fix it?  Like I stated above, when it works it works great...the hardware and firmware must be capable...I hope it's not just a fluke.  I'd rather be using my Sundays doing things I enjoy.

@benjaminAU 

And which is the power adapter?

@Woodszer 

I replaced it with one I got off Amazon for a different application a few months back.   From my order - Aclorol 12V 10A 120W Power Supply Adapter AC 100-240V to DC 12volts 10amps Universal Switching Power 5.5X2.1mm, compatible with 5.5X2.5mm.

I don't think you need 10A as the stock one that comes with the AX6000 is 4 amps; maybe a six amp supply will fix that part of the problem.  The Aclorol supply is cleaner, at least according to my oscilloscope, than the ship-with supply but that's a sample of only one of each.

@GOATMAN42 

When your router restart. The systemtools time changed on the firmware date?

The new power supply solved the problem?

@Woodszer 

I'm not quite sure what you're asking but the time the router thinks it is is correct.   I'm not real sure if that's because I have a stratum 1 network time server (and GPSDO) on my local network for RF communications gear or it's stable through the reboot.  The router and nodes on the local network do not need an Internet connection to maintain good time; the time server both broadcast the time and provides a standard NTPD socket..

My router is currently still at 1.1.1 Build 20200714 rel.18254(5553);  I've been thinking seriously about updating to the latest (1.2.1 Build 20210205 rel.12759), even though it's got the "...you will be unable to downgrade..." warning.  Anyone here tried it?

@GOATMAN42 

I think random rebooting  is connected with antivirus database update when antivirus is on in your router. Switching off antivirus in router settings stopped unexpected rebooting. Probably the problem is with time settings between router and TrendMicro database because the date of last Update checking shows time in future in my timezone. 

@Woodszer changin the PS to another that with atleast 2A solved my issues.  TP support spend three days going back and forth asking me if the rounter is well ventelated, using the origional PS, if I had any failed firmware updates, if any lighting/storm. In the end to solve my issue, is to replace the power supply TP sent with my AX6000 with any other 12V with a minium 2A.  I don't expect TP to won up on this issue and replace their under power PS they shipped.