@meryfd I am sorry to report back that after not finding a solution to this issue, I finally returned the router to Amazon calling the tp-link warranty. I am so disapointed about it as I was quite...

I am trying the security settings suggested here to see if that improves the stability of the 2,4 GHz WiFi. I am still not running the beta firmware but the latest official version. Will report back...

I am also facing the same issue. The router (Archer C6(EU) v2.0) was quite stable with the same configuration over the firmware updates, but a month ago it started to drop the 2.4 GHz wifi band and...