watchdogd_flags followed by panic watchdog timeout, after reboot my rc.conf disappear

Hi all,
 
first of all, I´m sorry maybe for my bad English.
 
We have 2 routers which I maintain in our mesh wireless community network.
 
The Router 1 has 2 atheros adapters, ath0=wistron cm9, ath1=wistron cm10, of
course some sisX, fxpX and so on.
The Router 2 has 1 atheros adapter, ath0=wistron CM10.
 
My R1 panics and even more it freezes very often. Maybe the reason for
panicing and freezing is the same and maybe not.
 
This is not important now, this story is about R2.
 
I started to use "option SW_WATCHDOG" in both my custom kernels on the R1
and R2 recently in hope, it is some walkaround for freezing at least if not
for panicing.
 
In the /etc/defaults/rc.conf there are not "watchdogd_flags=""" option, but
I tried to wrote it to my /etc/rc.conf in this way:
 
watchdogd_enable="YES"
watchdogd_flags="-e ping 10.40.0.72 -s 2 -t 1"
 
I saved my rc.conf without any doubt.
 
I did so, because I wanted to instruct watchdogd to execute my command,
common pinging some IP address. I was not satisfied with a trivial file
system check instead.
 
After saving the rc.conf file, I restarted watchdogd deamon at once.
 
... and ... 2 seconds ... my ssh client was disconnected ... unexpected end
of ssh session. :)
 
Okay, maybe something wrong, maybe I did a mistake and it panicked.
 
I was waitting for 3 minutes, but R2 did not react at all.
 
So I went to R2 and I powered off and powered on ... but still it was the
same.
 
After I attached monitor and keyboard, I saw that ifconfig did not configure
any interfaces. Why ?
 
Answear: Because rc.conf had 0 Bytes !!!
 
-rw-r--r--  1 root  wheel      6174 Sep  1 XX:XX rc.conf , I do not remember
time of last modification of file.
 
So the content of rc.conf was completly gone !!!
 
Is it possible at all ?
 
Now I am scared that any modification rc.conf will be mean loss of content.
 
I have kernel dump and backtrace of panic.
 
It is in the attachment.
 
 
If I could help with this, I will do it.
 
And please explain me somebody, how I lost the content of rc.conf file. :-O
Thank you.
 
Daniel
 
P.S.: I am not currently subscribed in the freebsd-stable mailling list, so
use my e-mail address. I am ok with freebsd-current mailling list.