Do you use ethernet or WiFi as SSH-Connection? Ethernet (nano Pi NEO)
Do you use NetworkManager (nmtui) or /etc/network/interfaces for configuring the network-device? No, DHCP default
Did you try another SD-Card or did you check the SD-Card? (Type, Speed?) No, 8 GB Class10 Kingstick
Do you use a heat-sink? Or a case? 3D print Case + CPU heat-sink (not original)
I edited a file with vim and had 2-3 seconds no respondig, did not pay attention until this post from xgpt to it. But he hast bigger issues than me "... borking up and needing a restarted SSH session." I never had this problem.