WiFi devices but not being able to communicate between themselves again

Hey folks,

Seems this problem has cropped up again for me.

Presently running:

• RT-5300AC w/384.7_2
• ICMP snooping enabled for all bands (this is what fixed things last time)
• Tri-Band Smart Connect is enabled

WiFi to wired devices is fine, but WiFi to WiFi is problematic. I'm wondering if we're approaching the limit of what the 5300 can do? Connected to it is:

• WiFi 12+ devices
• Wired 6+ devices

It varies depending on who in the house has turned on...

WiFi devices but not being able to communicate between themselves again