good idea, the range should be much better than the current range.

It seems the only way to solve the issue is to disable the secure vault and use TP-Link Sharing account to secure it.

Do you mean KRACKs vulnerabiity? You can check the FAQ below: http://www.tp-link.com/en/faq-1970.html

Personally, no new firmware release means no big bug on this router in some ways.

Hi, which firmware did you upgrade to? You can have a try to downgrade the firmware or do some troubleshooting with TP-Link support. Perhaps you issue will be solved. I found a link for how to...

Here are the answers for your two questions. Hope they are helpful. 1. The IFTTT works for the whole mesh network, including the repeaters, not only the main router. 2. It is not recommended to turn...