That's really peculiar, as unchecking it should disable IPSec.
To be honest, I don't know what the setting does, as it's unique to the build of OpenWRT that we were provided from our chipset partner, but I'll try to find out what it's supposed to do.
My guess is that it enables the VPN server on the Almond+ and this might've caused some kind of issue if you were connecting to another IPSec server.