Why login to ssh/ftp 2 times on Debian 9?

Question

linux

Hello. We have a dedicated server, on AMD EPYC. We ran into a problem this year. On the Debian 9 Dedik, there were failures with connecting via sssh, ftp, even apache. The fact is that the connection works only the second time. That is, when entering through putty, it says that the connection is broken ... similarly, when connecting via FTP, it will connect only the second time. Reinstalling the system is not an option, a very huge amount of data ....

Answer 1

There is little information, the first thing I would start with is 2-way traffic dumps, maybe the problem is not on the server, but higher, + by chance there are no duplicate IPs on the network?