Port being stuck in PortServer TS 16

We use the PortServer TS 16 for serial ports connection. Sometimes, the serial port seems stuck in the PortServer. Below are some details when the issue happens:

  1. The port 6 is confused to be connected from telnet command;
  2. Checking the GUI in PortServer, it shows in the “Connections” that the Port 6 is listed in multiple columns in Active Network Connections being connected from a same server named as TEST_SERVER;
  3. Issuing “lsof -i -P” command on the server TEST_SERVER, there’s no open connections showing that this TEST_SERVER server is connected to port 6.

So is it the port 6 stuck in PortServer? Any possible reasons would cause this issue? Thanks.

Note that clicking “Disconnecting” in the “Action” column can often solve the issue.

Could anyone help with the issue here? Thanks in advance!