I have two Archer C7 V2 routers configured as hardwired access points, connected directly to my cable modem (modem is DNS server).   After 24 to 48 hours of operation, the 2.4 GHz band refuses connections.   It is only resolved after rebooting the C7s.   Both 2.4 GHz channels are set to WPA2/AES with 20 MHz channel widths.   One unit is on channel 1; the other on channel 11.   When I loose the 2.4 GHz, it is C7 specific (the other AP will continue to work for some period of time before failing).  Wired and 5GHz connections are very solid.

I previously configured one C7 as a router (router was DHS server) and the second as a wired access point from the router.   The same issue occurred in that configuration.  
This issue has been a recurrent problem for several years and I've always assumed it was a connected device failing the network.   After pushing as many devices as possible to either the 5 GHz channels or wired connections, I'm now at the point it has to be a router issue.  

I've seen older posts that indicated there was a firmware issue, but I'm running the most current version.  The firmware hasn't been updated on TP Link's website since 2018.   I've also seen posts where people are running open source firmware and am open to that if it resolves the issue.   Here is my most recent log where the connection failed

####################################################################
#                    Archer C7  System Log
# Time = 2016-01-02  1:55:31 93333s
# H-Ver = Archer C7 v2 00000000 : S-Ver = 3.15.1 Build 160719 Rel.57530n
# L = 192.168.0.203 : M = 255.255.255.0
# W1 = STATIC IP : W = 192.168.11.201 : M = 255.255.255.0 : G = 192.168.11.1
####################################################################

1st day 00:00:07    local_root=%s%s
    INFO       System started
1st day 00:00:12     SECURITY      INFO       PPTP Passthrough enabled
1st day 00:00:12     SECURITY      INFO       L2TP Passthrough enabled
1st day 00:00:12     SECURITY      INFO       IPSEC Passthrough enabled
1st day 00:00:12     SECURITY      INFO       FTP ALG enabled
1st day 00:00:12     SECURITY      INFO       TFTP ALG enabled
1st day 00:00:12     SECURITY      INFO       H323 ALG enabled
1st day 00:00:12     SECURITY      INFO       RTSP ALG enabled
1st day 00:00:12     SECURITY      INFO       SIP ALG enabled