In Netstat output, sometimes an ESTABLISHED or LISTEN entry is missing

Issue

• We have a small script calling netstat command to identify socket ESTABLISHED connection
• From time to time that script would report a 'false positive' that an ESTABLISHED connection is missing
• After some debugging and extra logging we have identified that this is not the case and to prove it replaced the script with ss command.
• This proved that the issue was only in the output of netstat.
• Can you please clarify what could be the reason for the files in /proc/net/tcp not being written or accessible by the netstat command at the time of its execution?
• We found that when executing 'netstat -na', very rarely a LISTEN-state socket is missing from the output. The port is contained in the pure output of cat /proc/net/tcp.