@Brian2700  I'm having the same issue but on their download page it says you can't rollback.  This behavior is completely unacceptable as I and my wife work from home.  If they can't get us a solution soon I may be forced to buy a new router(wasted money).  This is ridiculous from a support perspective.

  @BrianThoms 

Here is a beta firmware for Deco X55 1.2. You could test whether it helps:

https://community.tp-link.com/en/home/forum/topic/734426

  @A-Deco-user I have installed this beta firmaware and been running it for a few days now and it seems to have fixed the issue with contantly releasing WAN/dropping internet for 20 secs or so. I installed on 2 of the 3 devices and have been streaming TV and other items with no issues.

Downside about 2-3 weeks too late as i had to purhcase a new router as this was affecting my ability to work as me and wife both work from home.  

Just an update for anyone searching for a solution to the WAN connection drops I've described above with firmwarever 1.4.0, the beta firmware available on the forum for the Deco X55 resolved the issue.