First Floor is a Fritzbox 7390 with the rest of the Lan.
Gargoyle is configured like this:
Fritzbox IP=192.168.3.1 (no dhcp server active)
Debian Server IP= 192.168.3.69 (with dhcp dnsmask,tftp etc.)
Bridge IP= 192.168.3.2
Netmask = 255.255.255.0
AP/Gateway IP= 192.168.3.1
Wan Ethernet port = Disabled
Nameserver= Use Gateway
Repeater enabled
Operation mode n+g+b
Channel width 40MHz
Transmit Power Max
SSID to join fritzzz (from frtzbox)
SSID Gargoyle
Channel 11 (is fixed in fritzbox)
Encryption Wpa2 psk
password very_secret

So everything is working fine, until some wireless client logs into Gargoyle
a couple of seconds later there is no device behind the gargoyle router and also gargoyle router itself not to ping.
I have to reboot the gargoyle router to get it work again.
As workaround I have disabled repeater an only use the bridge.
But so I have no wireless in the Kitchen

I suppose ther might be a bug in iptables script????
Don' know.
with 1.6.0 I had the same Problem. Earlier version I don#t know because
I had them in ap mode connected throug Dlan.