@Carl I don't really want to delay this issue any longer, I'm having a lot of difficulties at home with this situation and my security devices are not working to protect my home. I need this to be resolve right now and I don't think any further test would figure out the problem.

@Carl ive been running the beta firmware for quite a while. I still have to reboot every day to maintain speeds north of 800mbps. So I don't believe the actual fix is in just quite yet for the beta firmware. 
 

I do sqa testing professionally- if there is anything I can do to assist I'm willing to help out. If I were testing this product out and o knew about with these complaints, I'd find a way to get the engineers to log more data to help narrow the issue down. Because a reboot resolves the issue temporarily there's a leak somewhere that needs to be found.

What I can tell you is that when I see the issue I also see that the cpu usage is around 14-30% on one of the cores instead of 2-5% evenly distributed across the cores.

what I'd like to see at a minimum is an official firmware release that removes the beta background. 
 

@Carl 

If you were refering me about the user who claimed that issue been addressed, then I have to say I'm sorry. It only works after I reboot the router. The problem still there. That's is a compromised solution for the problem.

@Carl 

I am thankful that at least communication is improving at this time. I do have to wonder how many users actually have gigabit speeds to see the problem though. It might just be that it doesn't appear with lower speeds (even as high as 400 might not see it as that's where I seem to average) as likely most users will have.

Carl, Just got Frontier to install 500mbps/Mbps at our location, i have a direct WAN line connected to the archer 5400x. Note: using default router that comes with frontier, i can get >500mbps, and using the direct Ethernet from the modem to the pc i can also get 500mbps. When plugging the wan ethernet to the archer, ALL LAN Hardwires are capped at 100mbps, regardless of the ports on the back of router. I changed speed negotiations to 1gbps, on my device and also router settings and still nothing new. What can we do in this case? I also tried factory reset, reboot, and power cycling. I CAN however, get >500 MBPS on wireless, but it defeats the purpose of me having wires on every computer and some devices i will run with a switch.

I also tried the beta firmware, and the newest firmware available on the support page, and neither make a difference.

@Carl 

Ive been having a similar (if the the exact same) issue. It's not noticable if you have fast enough internet doing everyday tasks but the wired connections in the rear seem to heavily limit my speeds.

When testing from the router I get my expected speeds

Down- 232.9Mbps

Up- 12.5Mbps

However at the computer (only device currently connected to the network) that's using a wired connection I get

Down- 129.2Mbps

Up- 0.65Mbps

Under normal conditions we didn't notice a problem UNTIL we went to do a Livestream broadcast and that upload speed really showed it's colors. That's when we started troubleshooting.

We've had to go back to using our cheap old router in the meantime (which is working normally and giving our normal speeds).

I think the only reason you might not be hearing more about this is because it may go overlooked by most people.