First off, thank you LEDE devs for supporting my newer router TL-842N v3. DD-WRT is still lagging on that one.
Now the question - I enabled "Disable EAPOL Key Retries" in the latest version, and my Android phone started losing WiFi connection a few minutes after screen turned off. When you wake it up, the WiFi quickly reconnected, but this behavior was clearly bad because even a background Youtube video would shift from WiFi to cellular data plan when the screen is off.
So I fiddled with LEDE settings and discovered that switching wireless to LEGACY and turning off WMM fixed this problem. The "Disable EAPOL..." option is still ON, and yet I don't have the phone losing connection problem.
I am fine with downgraded 54mbps speed. I just want to know, did this really fix the issue, or did I stumble upon a bug where this combination of settings stealthily DISABLES "Disable EAPOL Key Retries" option, which is why its side-effect is gone?