I have three customers I set up with deco P9 v1s several years ago, all of which have had problems develop since the firmware update in August. 

Symptoms I've seen. 

-Frequent 'failed to save information' messages when trying to update via the app. 

-Decos losing communication when before the update they were stable. 

-Decos with white lights and working where the app says they're offline ('check again' does not find them)

-Direct access to web interface via 192.168.1.1 is slow/unreliable, often taking multiple refreshes of the page.

-Sporadic behaviour with TP-link DDNS (doesn't update/loses information) 

One of the networks has since been replaced, but the other two remain very unstable. 

Thanks for your help.