Because I'm a unique jerk and I write terribly not sloppy and ill-considered code, I managed to leave my hosting machine without access for the whole evening. The problem turned out to be trivially stupid, but who cares in time.

#!/bin/bash -x
wget -O /tmp/ipaddr
IPADDR=$(cat /tmp/ipaddr | grep -Eo '\<[[:digit:]]{1,3}(\.[[:digit:]]{1,3}){3}\>')
IPADDROLD=$(cat /tmp/ipaddr_old | grep -Eo '\<[[:digit:]]{1,3}(\.[[:digit:]]{1,3}){3}\>')

if [ "$IPADDR" != "$IPADDROLD"  -a "$IPADDR" != "" ]
 sed -i "s/[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}/$IPADDR/" /etc/bind/
 /etc/init.d/bind9 restart
 echo "server localhost" > /tmp/nsupdate
 echo "zone" >> /tmp/nsupdate
 echo "update delete A" >> /tmp/nsupdate
 echo "update delete CNAME" >> /tmp/nsupdate
 echo "update add 38400 A $IPADDR" >> /tmp/nsupdate
 echo "update add * 38400 CNAME" >> /tmp/nsupdate
 echo "show" >> /tmp/nsupdate
 echo "send" >> /tmp/nsupdate
 echo "" >> /tmp/nsupdate
 /usr/bin/nsupdate -k /etc/ -d /tmp/nsupdate
 mv /tmp/ipaddr /tmp/ipaddr_old

This is already a fixed script that will not allow an error. In a moment I will explain where the problem was, now I will explain what the script does. At least I'm on a dynamic public ip. I have run the above script to check for a change in my address if it changes to change the machine settings and send information about my domain, that there is a change. Generally a trivial script, but in it I had made a terribly stupid omission. In the part where it is checked for change of address

if [ "$IPADDR" != "$IPADDROLD"  -a "$IPADDR" != "" ]

It used to be

if [ "$IPADDR" != "$IPADDROLD"]

So the line itself does the following, takes the 2nd IP addresses and checks them if they are the same skips if they are different updates. In the previous version I had missed a very important error for some reason my script had decided that I have IP = “” (nothing) and rewrote the configuration of my bind with an empty field and on the next change it can no longer rewrite the configuration correctly which leads to a lack of connection with the nameservr. It's stupid, isn't it?