@JoeG 

Once the router was updated, how long was the CPU at 90+%? Or how long did you leave the router alone?

Did you do a factory default with the new firmware to see if the CPU usage dropped?

Were you able to see the system logs while the high CPU usage was happening?

The router had been running for at least 6 hours after it was updated.  I only noticed it many hours later, after using the internet all day.  It was above 90%, never went below.  I watched it like this for at least 10 minutes with no one using the wifi, just me on my hard-wire connection.  My settings remained in the router after I updated (but when I reverted to the previous version, they were erased, and I had to restore from a backup file.)  I did look at the system logs but did not see anything unusual.  I have been using the previous version now for days, and it is stable.

@JoeG 

HQ has been made aware of the issue you brought up.

We had local testers look into it, but could not replicate it.

Regardless, when we get new information we will follow up.

You state that you cannot replicate the issue.  I have received an email from tp-link saying that they have replicated the issue:

"After testing in our lab, thanks to your feedback, and we have reproduced this problem. Besides, we have feedback it to our R&D Department and make an improvement in our later firmware versions to fix it.-- Myra.Niu TP-LINK Technical Support"

So I am waiting to hear further from tp-link.

Was this resolved? I am also experiencing the same issue. 

We are aiming to release a firmware fix within the next month or less to resolve the UI issue.

Can you also fix the issue of not reconizing GPT volumes more than 2? I have a EFI windows 10 hard drive but the router can only recognize the recovery partition and volume2 but can not read the OS partition. This is using the USB port to External Drive to GPT EFI windows 10 SATA NTFS. This drive has windows 10 and 3 partitions, 1TB

Experiencing the same issue as the OP.  But, what are the actual consequences of high CPU usage, other than perhaps making the device run warmer than is normal?

@john_hamster 

The high CPU usage is a UI issue meaning the display indicates it is high, but it is not. New firmware that will be released aims at resolving that.

I am also experiencing the same issues after the update.  I am trying to revise settings to the router and the router keeps freezing up.  Hoping there is an updated firmware solution soon!